Science Quizzes

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CHEMISTRY #3681

Describe how chlorine gas is prepared in the laboratory using manganese(IV) oxide. Write the equation.

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CHEMISTRY #3687

Explain the bleaching action of chlorine. How does it differ from that of sulphur dioxide?

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CHEMISTRY #3690

Describe the "fountain experiment" and what it demonstrates.

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CHEMISTRY #3697

Explain why chlorine water loses its color and bleaching power when exposed to sunlight.

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CHEMISTRY #3698

A student prepares chlorine using KMnO₄ and HCl. Why is this reaction faster than using MnO₂?

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CHEMISTRY #3699

Why is sodium hypochlorite manufactured using cold, dilute NaOH, not hot concentrated NaOH?

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CHEMISTRY #3701

Explain why dry hydrogen chloride gas does not turn blue litmus red, but hydrochloric acid does.

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CHEMISTRY #3702

Why is hydrochloric acid considered a strong acid but not an oxidizing agent (dilute), while concentrated H₂SO₄ is both?

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CHEMISTRY #3704

Why is it dangerous to mix household bleach (containing NaOCl) with acidic toilet cleaners? What gas could be produced?

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CHEMISTRY #3705

Explain how chlorine is used to purify drinking water. What are the advantages and potential concerns?

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CHEMISTRY #3713

Bleaching powder is made by reacting chlorine with __________.

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CHEMISTRY #3715

Write balanced equation for preparation of chlorine from KMnO₄ and HCl.

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CHEMISTRY #3716

Write equation for reaction of chlorine with hot concentrated NaOH.

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CHEMISTRY #3722

What volume of chlorine gas at RTP (24 dm³/mol) from 43.5 g MnO₂?

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CHEMISTRY #3725

Compare and contrast properties and reactions of chlorine and hydrogen chloride. How would you distinguish them with chemical tests?

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CHEMISTRY #3726

Design a flow chart for industrial production of sodium hypochlorite from common salt, including electrolysis and subsequent reaction.

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CHEMISTRY #3727

Explain why chlorine is a powerful oxidizing agent, using its electron configuration and position in periodic table.

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CHEMISTRY #3728

Describe chemical tests (using chlorine water and organic solvent) to identify NaCl, NaBr, and NaI.

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CHEMISTRY #3729

How is reaction between Cl₂ and NaOH used to make both bleach and chlorates? What conditions determine product?

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CHEMISTRY #3730

Why is it important to store bleach in opaque (dark) containers? Write the decomposition equation.

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CHEMISTRY #3731

Explain why chlorine can displace bromine from KBr, but iodine cannot displace chlorine from KCl.

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CHEMISTRY #3738

Using standard reduction potentials, explain why Cl₂ displaces Br⁻ but Br₂ cannot displace Cl⁻.

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CHEMISTRY #3739

Name two other oxidizing agents that can be used to generate chlorine gas from HCl.

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CHEMISTRY #3742

Excess chlorine reacts with ammonia to form __________ which is explosive.

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CHEMISTRY #3743

Chloramine (NH₂Cl) is used as a disinfectant instead of chlorine because it produces fewer __________ by-products.

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CHEMISTRY #3747

What are the three main products of brine electrolysis and how are they separated?

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CHEMISTRY #3748

In the __________ cell for brine electrolysis, a cation-exchange membrane separates the anode and cathode compartments.

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CHEMISTRY #3749

Why are mercury cells for chlorine production being phased out?

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CHEMISTRY #3750

Chlorination of water containing organic matter can produce __________ which are potentially carcinogenic.

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CHEMISTRY #3751

What is the approximate formula of bleaching powder?

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CHEMISTRY #3752

Write the equation for reaction of bleaching powder with dilute acid.

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CHEMISTRY #3753

In the mercury cell, sodium forms an __________ with mercury at the cathode.

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CHEMISTRY #3754

Compare chlorine, hydrogen peroxide, and sulfur dioxide as bleaching agents.

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CHEMISTRY #3758

What are the oxidation states of chlorine in Cl₂, HOCl, ClO₂⁻, ClO₃⁻, ClO₄⁻?

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CHEMISTRY #3759

__________ dioxide (ClO₂) is used as a more environmentally friendly bleaching agent for paper pulp.

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CHEMISTRY #3760

Write the equation for reaction of chlorine with sodium thiosulfate (used to dechlorinate water).

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CHEMISTRY #3761

Describe the Frasch process for extracting sulphur. Why is this method used?

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CHEMISTRY #3765

State two chemical properties of SO₂, with equations.

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CHEMISTRY #3768

List the optimum conditions for the Contact Process and explain why they are chosen.

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CHEMISTRY #3769

Why is SO₃ not absorbed directly into water to make sulphuric acid?

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CHEMISTRY #3771

Explain why rhombic sulphur is stable at room temperature, while monoclinic sulphur is stable above 96°C.

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CHEMISTRY #3773

Why is sulphur dioxide collected by upward displacement of air, not over water?

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CHEMISTRY #3774

Explain the bleaching action of sulphur dioxide. How does it differ from chlorine bleaching?

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CHEMISTRY #3775

Why is 450°C used instead of a lower temperature that would give higher equilibrium yield of SO₃?

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CHEMISTRY #3777

Write equations for concentrated H₂SO₄ with: a) Copper, b) Sugar, c) NaCl, d) KNO₃.

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CHEMISTRY #3780

How does sulphur dioxide contribute to acid rain? Write the equations involved.

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CHEMISTRY #3786

SO₃ is absorbed in __________ to form oleum.

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CHEMISTRY #3792

Write equation for reaction of SO₂ with hydrogen sulfide.

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CHEMISTRY #3794

Write equation for formation of oleum.

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CHEMISTRY #3795

Write equation for dilution of oleum to form sulphuric acid.

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CHEMISTRY #3796

Write equation for reaction of concentrated H₂SO₄ with carbon.

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CHEMISTRY #3797

Calculate mass of sulphur needed to produce 100 kg of H₂SO₄ (98% yield assumed? Actually 100% yield). S=32, H₂SO₄=98.

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CHEMISTRY #3798

What volume of SO₂ at RTP (24 dm³/mol) from 6.3 g Na₂SO₃ (M=126) with excess HCl?

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CHEMISTRY #3799

If 100 g SO₂ is converted to SO₃ with 98% yield, mass of SO₃ produced? SO₂=64, SO₃=80

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CHEMISTRY #3800

Calculate mass of H₂SO₄ produced from 100 g oleum (H₂S₂O₇). H₂S₂O₇=178, H₂SO₄=98.

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CHEMISTRY #3801

Compare and contrast allotropes of carbon (diamond, graphite) with allotropes of sulphur.

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CHEMISTRY #3802

Design a flow chart for industrial production of H₂SO₄ from elemental sulphur.

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CHEMISTRY #3803

Explain why H₂SO₄ is both an acid and an oxidizing agent. Give examples of each.

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CHEMISTRY #3804

Describe chemical tests to identify Na₂SO₃, Na₂SO₄, and Na₂CO₃.

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CHEMISTRY #3805

How does combustion of S-containing fossil fuels lead to acid rain, and how can it be mitigated?

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CHEMISTRY #3806

Why is V₂O₅ used as catalyst in Contact Process? What happens if catalyst is poisoned?

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CHEMISTRY #3807

Using equilibrium and kinetics, explain why Contact Process conditions are a compromise.

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CHEMISTRY #3808

Write the equation for SO₂ reducing acidified K₂Cr₂O₇.

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CHEMISTRY #3810

What is the chemical formula of oleum?

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CHEMISTRY #3811

The biological process where sulphur compounds are oxidized or reduced by microbes is called the __________ cycle.

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CHEMISTRY #3814

The reaction of SO₃ with HCl produces .

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CHEMISTRY #3817

When molten sulphur is poured into cold water, it forms a rubbery form called __________ sulphur.

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CHEMISTRY #3818

What happens to the colour of molten sulphur as it is heated from 120°C to 180°C?

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CHEMISTRY #3819

Why does the viscosity of molten sulphur decrease at very high temperatures (>200°C)?

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CHEMISTRY #3586

Define: a) Standard enthalpy of formation (ΔH°f) b) Standard enthalpy of combustion (ΔH°c) c) Standard enthalpy of solution (ΔH°sol)

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CHEMISTRY #3589

Write the equation relating enthalpy of solution, lattice energy, and hydration energy.

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CHEMISTRY #3590

Explain why magnesium oxide has a much more negative lattice energy than sodium chloride.

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CHEMISTRY #3592

Why do we use Hess's Law to calculate enthalpy changes that cannot be measured directly?

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CHEMISTRY #3593

Ammonium nitrate dissolves in water and the solution becomes cold. Explain in terms of lattice energy and hydration energy.

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CHEMISTRY #3594

Sodium hydroxide dissolves in water and the solution becomes hot. Explain in terms of lattice energy and hydration energy.

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CHEMISTRY #3596

Explain why lattice energy of MgO is much larger than NaCl. Refer to ionic charges and radii.

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CHEMISTRY #3597

Why does KCl have a less exothermic lattice energy than NaCl?

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CHEMISTRY #3598

Explain why hydration energy of Al³⁺ is much more negative than that of Na⁺.

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CHEMISTRY #3599

Student measures temperature decrease when NH₄Cl dissolves. Infer relative magnitudes of lattice and hydration energy.

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CHEMISTRY #3609

Calculate ΔH for 2C(s) + H₂(g) → C₂H₂(g) given: ΔH°c C(s) = -394 kJ/mol, ΔH°c H₂(g) = -286 kJ/mol, ΔH°c C₂H₂(g) = -1300 kJ/mol.

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CHEMISTRY #3611

Calculate ΔH°f C₃H₈(g) given: ΔH°c C(s) = -394, ΔH°c H₂(g) = -286, ΔH°c C₃H₈(g) = -2220 kJ/mol.

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CHEMISTRY #3612

Calculate lattice energy of KCl given: ΔH°f KCl(s) = -437, ΔHsub K(s)=+89, IE K=+419, BE Cl₂=+244 (per mole Cl₂, so ½=+122), EA Cl=-349 kJ/mol.

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CHEMISTRY #3613

Calculate ΔHsol of KCl: lattice energy = -715 kJ/mol, hydration K⁺ = -322, hydration Cl⁻ = -364 kJ/mol. Explain sign.

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CHEMISTRY #3614

Calculate lattice energy of MgO given: ΔH°f MgO(s) = -602, ΔHsub Mg(s)=+148, IE₁=+738, IE₂=+1450, BE O₂=+498 (½=+249), EA₁=-141, EA₂=+798 kJ/mol.

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CHEMISTRY #3615

Draw and label a Born-Haber cycle for formation of sodium chloride from elements.

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CHEMISTRY #3616

Explain why the second electron affinity of oxygen is positive (endothermic), while the first is negative.

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CHEMISTRY #3617

Compare factors affecting lattice and hydration energy. How do they determine whether salt dissolves exothermically or endothermically?

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CHEMISTRY #3618

Why is ΔH neutralization for HCl + NaOH ≈ -57 kJ/mol, constant for most strong acid-strong base reactions?

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CHEMISTRY #3619

How does Hess's Law allow determination of benzene ΔH°f, which cannot be made directly from its elements?

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CHEMISTRY #3624

Why can't the enthalpy of formation of CO be measured directly?

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CHEMISTRY #3625

What is resonance energy? How does it relate to enthalpy?

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CHEMISTRY #3630

Why is the enthalpy change of neutralization for any strong acid and strong base approximately the same?

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CHEMISTRY #3634

How does Born-Haber cycle for MgCl₂ differ from NaCl?

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CHEMISTRY #3651

Name two sources of error in calorimetry experiments.

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CHEMISTRY #3662

The enthalpy change when one mole of gaseous atoms is formed from an element is called enthalpy of __________.

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CHEMISTRY #3666

Why is a bomb calorimeter used for combustion reactions instead of a simple polystyrene cup?

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CHEMISTRY #3669

For reactions at constant pressure, ΔH = q_p; at constant volume, ΔU = q_v. Which is bomb calorimeter?

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CHEMISTRY #3672

The enthalpy change when 1 mole of precipitate forms from its ions in solution is called enthalpy of __________.

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CHEMISTRY #3673

Why does NH₄NO₃ dissolve endothermically even though lattice energy is very exothermic?

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CHEMISTRY #3559

Student plots V vs T(°C) for Charles's law, line extrapolates to -273°C. What does this represent? Why significant?

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CHEMISTRY #3568

State Gay-Lussac's law of combining volumes.

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CHEMISTRY #3570

What volume of H₂ at STP from 6.5 g Zn with excess HCl? Zn + 2HCl → ZnCl₂ + H₂ (Zn=65)

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CHEMISTRY #3572

The root mean square speed (u_rms) of gas molecules is √(3RT/M). This shows u_rms is inversely proportional to √M, consistent with __________ law.

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CHEMISTRY #3573

Why do real gases deviate from ideal gas behavior at high pressure and low temperature?

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CHEMISTRY #3574

What correction does the van der Waals equation add to the ideal gas law?

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CHEMISTRY #3532

Why do weather balloons expand as they rise to higher altitudes? (Consider both pressure and temperature changes.)

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CHEMISTRY #3535

Explain how Graham's law can be used to determine the molar mass of an unknown gas.

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CHEMISTRY #3545

Gas has volume 2.0 L at 25°C. To what temperature (°C) must it be heated to triple volume, pressure constant?

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CHEMISTRY #3546

Gas occupies 400 cm³ at 27°C and 100 kPa. Calculate volume at 127°C and 200 kPa.

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CHEMISTRY #3548

150 cm³ oxygen diffuses in 30 seconds. Time for 150 cm³ hydrogen (H₂=2, O₂=32)?

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CHEMISTRY #3550

A gas diffuses 2.0 times slower than oxygen. Approximate molar mass?

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CHEMISTRY #3551

Gas occupies 250 mL at 30°C and 700 mmHg. Volume at STP (0°C, 760 mmHg)?

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CHEMISTRY #3552

100 mL N₂ diffuses in 50 s. Time for 100 mL unknown gas (M=64 g/mol) under same conditions? (N₂=28 g/mol)

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CHEMISTRY #3553

Bubble at lake bottom: T=8°C, P=2.8 atm, V=15 cm³. Surface: T=25°C, P=1.0 atm. Volume at surface?

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CHEMISTRY #3554

Cylinder: 20 L gas at 15 atm, 27°C. After use: P=5 atm, T=17°C. Volume remaining at final conditions? Volume used at STP?

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CHEMISTRY #3555

Compare assumptions behind Boyle's, Charles's, and Graham's laws in terms of kinetic molecular theory.

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CHEMISTRY #3556

Porous pot with air connected to manometer. When jar of H₂ placed over it, water level moves. Explain.

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CHEMISTRY #3557

Using combined gas law, derive expression for gas density as function of P and T.

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CHEMISTRY #3458

Explain why limewater turns milky with CO₂, and why the milkiness disappears with excess CO₂.

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CHEMISTRY #3459

How is carbon monoxide prepared in the lab? Write the equation.

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CHEMISTRY #3462

Give two uses of CO as a reducing agent.

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CHEMISTRY #3464

Outline the main processes in the carbon cycle.

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CHEMISTRY #3467

Why is graphite used as a lubricant in machinery, even at very high temperatures?

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CHEMISTRY #3469

Why is hydrochloric acid preferred over sulfuric acid for preparing CO₂ from marble chips in the lab?

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CHEMISTRY #3470

Magnesium continues to burn in a jar of carbon dioxide. Explain this observation and write the equation.

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CHEMISTRY #3472

Why is carbon monoxide considered a good reducing agent? Give an example of its use in industry.

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CHEMISTRY #3473

Explain why sodium carbonate does not decompose on heating, but calcium carbonate does.

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CHEMISTRY #3475

How does the carbon cycle help regulate the Earth's temperature? What happens when this balance is disturbed?

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CHEMISTRY #3492

Write equation for reaction of carbon monoxide with iron(III) oxide.

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CHEMISTRY #3494

Write equation for reaction of potassium hydrogen carbonate with sulfuric acid.

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CHEMISTRY #3496

What volume of CO₂ (at RTP) is produced when 25 g CaCO₃ reacts with excess HCl? (1 mole gas at RTP = 24 dm³; CaCO₃ = 100 g/mol)

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CHEMISTRY #3498

Compare and contrast properties and uses of diamond and graphite. Explain how structures determine properties.

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CHEMISTRY #3499

Design a flow chart showing how carbon is cycled through atmosphere, biosphere, hydrosphere, lithosphere. Label key processes.

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CHEMISTRY #3500

Explain why burning fossil fuels increases greenhouse effect. Describe two consequences of global warming.

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CHEMISTRY #3501

A mixture of CaCO₃ and CaO. Describe a chemical test to prove both are present.

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CHEMISTRY #3502

Why is carbon monoxide considered a secondary pollutant? How is it formed in urban environments?

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CHEMISTRY #3504

Predict products and write equations for: a) NaHCO₃ + HNO₃ b) ZnCO₃ + heat c) CO₂ + KOH d) CO + CuO + heat

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CHEMISTRY #3505

What is the formula of buckminsterfullerene (buckyball)?

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CHEMISTRY #3506

What is graphene? List two of its remarkable properties.

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CHEMISTRY #3510

Explain in detail why diamond is an electrical insulator.

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CHEMISTRY #3511

Give a potential application of fullerenes (buckyballs).

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CHEMISTRY #3512

Which carbon reservoir is largest?

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CHEMISTRY #3513

What causes ocean acidification? Write the equation.

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CHEMISTRY #3515

The ability of a gas to trap heat compared to CO₂ is called its potential.

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CHEMISTRY #3516

List three ways to reduce CO₂ emissions from human activities.

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CHEMISTRY #3520

Explain why lime mortar (Ca(OH)₂) hardens over time when exposed to air.

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CHEMISTRY #3390

What is the purpose of using cryolite in the extraction of aluminium?

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CHEMISTRY #3394

Why are graphite electrodes often used in electrolysis? Why must they be replaced regularly in the aluminium extraction process?

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CHEMISTRY #3395

Explain why during electrolysis of dilute H₂SO₄, volume of H₂ is twice volume of O₂. Write half-equations.

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CHEMISTRY #3397

Why is pure copper essential for electrical wiring? How is impure copper purified using electrolysis?

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CHEMISTRY #3398

In electrolysis of concentrated NaCl solution (brine), why is H₂ produced at cathode instead of Na?

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CHEMISTRY #3399

Explain the difference between electrolysis of molten NaCl and aqueous NaCl.

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CHEMISTRY #3400

During purification of copper, what happens to impurities like gold and silver? Why is this economically important?

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CHEMISTRY #3411

Write half-equation for formation of oxygen gas at the anode from hydroxide ions (OH⁻).

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CHEMISTRY #3414

A current of 2.0 A is passed through molten NaCl for 30 minutes. Calculate mass of Na produced. (F = 96500 C mol⁻¹, Na = 23; Na⁺ + e⁻ → Na)

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CHEMISTRY #3415

During copper purification, current of 10 A passed for 2 hours. Mass of Cu deposited at cathode? (Cu=63.5, Cu²⁺ + 2e⁻ → Cu)

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CHEMISTRY #3418

Write the overall equation for electrolysis of concentrated sodium chloride solution (brine).

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CHEMISTRY #3419

Compare and contrast electrolysis of molten NaCl and aqueous NaCl. Include products, half-equations, and explanations.

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CHEMISTRY #3420

Explain why extraction of aluminium is so expensive. List at least three factors.

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CHEMISTRY #3422

Predict products of electrolysis for concentrated potassium iodide solution. Justify using ion discharge tendencies.

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CHEMISTRY #3423

Why is it important to use direct current (DC) for electrolysis, not alternating current (AC)?

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CHEMISTRY #3424

Explain how reactivity series determines extraction method for iron (carbon reduction) and aluminium (electrolysis).

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CHEMISTRY #3425

Why is it important to keep chlorine gas separate from H₂ and NaOH in brine electrolysis? What would happen if mixed?

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CHEMISTRY #3426

Explain how sacrificial protection (using zinc) works to prevent rusting, and how it differs from electroplating.

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Completed

CHEMISTRY #3427

What is the discharge series (electrochemical series) in electrolysis?

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CHEMISTRY #3428

Predict the products for electrolysis of concentrated copper(II) sulfate solution using inert electrodes.

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CHEMISTRY #3434

Cryolite used in aluminium extraction has the formula __________.

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CHEMISTRY #3435

Explain why graphite anodes need frequent replacement in aluminium extraction.

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CHEMISTRY #3436

Predict products for electrolysis of dilute sodium sulfate solution using inert electrodes. Why?

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CHEMISTRY #3437

Describe how to gold-plate a brass ring using electrolysis. Include electrolyte and half-equations.

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CHEMISTRY #3441

What is Faraday's First Law of Electrolysis?

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CHEMISTRY #3442

The more easily an ion is discharged, the __________ its position in the electrochemical series.

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CHEMISTRY #3443

A solution contains NaBr and CuSO₄. Predict the initial products at each electrode.

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CHEMISTRY #3445

The industrial extraction of aluminium is called the - process.

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CHEMISTRY #3446

What environmental problems are associated with aluminium extraction?

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CHEMISTRY #3221

Explain why the first ionization energy of Al (578 kJ/mol) is slightly lower than Mg (738 kJ/mol).

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CHEMISTRY #3222

Why is there a slight drop in ionization energy between phosphorus and sulfur? (P: [Ne]3s²3p³, S: [Ne]3s²3p⁴)

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CHEMISTRY #3223

Arrange ions in increasing ionic radius: Mg²⁺, O²⁻, F⁻, Na⁺, Al³⁺. Explain.

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CHEMISTRY #3224

Explain why fluorine has a higher electronegativity than chlorine, even though chlorine has more protons.

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CHEMISTRY #3228

Explain why Al³⁺ ionic radius is much smaller than Na⁺, even though both are in same period.

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Completed

CHEMISTRY #3238

Why is there a drop in IE from Mg (738) to Al (578)?

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CHEMISTRY #3239

Why is there a drop in IE from P (1012) to S (1000)?

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CHEMISTRY #3241

Explain difference: Na⁺ (102pm) vs Mg²⁺ (72pm).

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CHEMISTRY #3242

Explain difference: F⁻ (133pm) vs O²⁻ (140pm).

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CHEMISTRY #3243

Predict and explain trends in EN and IE for Group I (Li to Fr) and across Period 2 (Li to Ne).

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Completed

CHEMISTRY #3245

Explain why second ionization energy is always higher than first. Use sodium as example.

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CHEMISTRY #3246

Compare atomic and ionic radius trends across Period 3. Why is ionic radius change more dramatic from cations to anions?

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CHEMISTRY #3248

Explain why ionization energy of oxygen is lower than nitrogen, despite higher nuclear charge.

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CHEMISTRY #3249

How do IE and EN trends explain why metals form cations and non-metals form anions?

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CHEMISTRY #3253

Define effective nuclear charge (Z_eff).

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CHEMISTRY #3267

Compare oxygen and sulfur: a) atomic radius b) IE c) EN d) reactivity.

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CHEMISTRY #3268

Use periodic trends to explain why chlorine displaces bromine from bromide solution, but bromine cannot displace chlorine from chloride solution.

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CHEMISTRY #3270

Mendeleev predicted properties of undiscovered elements using periodic trends. Explain how.

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CHEMISTRY #3272

Order P, S, Cl by increasing first ionization energy.

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CHEMISTRY #3283

What unique property do transition metals (d-block) have due to their electron configuration?

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CHEMISTRY #3284

Order these isoelectronic species (all 10 electrons) by increasing radius: Mg²⁺, Na⁺, Ne, F⁻, O²⁻.

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Completed

CHEMISTRY #3291

Why does the first element in each group (Li, Be, B, C, N, O, F) often show anomalous properties?

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CHEMISTRY #3292

What is the diagonal relationship in the periodic table?

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CHEMISTRY #3293

State one similarity between beryllium (Be) and aluminium (Al) (diagonal relationship).

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CHEMISTRY #3296

Why are atomic radii of noble gases larger than expected for their period?

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CHEMISTRY #3299

Why is the atomic radius of Ar (154 pm) larger than Cl (99 pm) even though Ar is to the right?

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CHEMISTRY #3131

Explain why diamond is very hard but graphite is soft.

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CHEMISTRY #3132

Why does graphite conduct electricity but diamond does not?

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Completed

CHEMISTRY #3133

Explain why MgO has a higher melting point than NaCl.

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CHEMISTRY #3134

A substance is solid at RT, very high MP, does not conduct electricity in any state. What type of structure?

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CHEMISTRY #3136

Water is liquid at RT, H₂S is gas. Both simple molecular. Suggest reason.

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CHEMISTRY #3137

Why is graphite used as lubricant in machinery, even at high temperatures where oil would burn?

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CHEMISTRY #3139

SiO₂ has high MP and is hard; CO₂ is gas at RT. Both Group IV oxides. Explain.

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CHEMISTRY #3143

Explain why ionic compounds are brittle. What happens when a force is applied?

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CHEMISTRY #3158

Describe the dot-and-cross diagram for carbon dioxide (CO₂) showing double bonds.

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CHEMISTRY #3159

Describe the dot-and-cross diagram for nitrogen (N₂) showing triple bond.

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CHEMISTRY #3163

Compare and contrast diamond and graphite. Why are they both carbon but have different uses?

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CHEMISTRY #3164

A new material is extremely hard, conducts electricity, high MP. Suggest structure type. Could it be a form of carbon?

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CHEMISTRY #3165

Explain why NaCl dissolves in water but SiO₂ (sand) does not.

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CHEMISTRY #3166

Why is ice less dense than liquid water?

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CHEMISTRY #3167

Predict properties of a giant covalent structure with delocalized electrons (like graphite).

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CHEMISTRY #3168

Using bonding concepts explain: a) Copper for wires b) Diamond for drill tips c) Graphite in pencils d) Argon as inert atmosphere.

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CHEMISTRY #3169

Design a table comparing ionic, simple covalent, giant covalent, and metallic substances.

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CHEMISTRY #3179

A covalent bond where both shared electrons come from one atom is called a __________ covalent bond.

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CHEMISTRY #3181

What is graphene?

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CHEMISTRY #3182

What is the formula of the buckminsterfullerene molecule?

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CHEMISTRY #3183

What does VSEPR theory state?

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CHEMISTRY #3190

Explain why metals feel cold to touch even at room temperature.

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CHEMISTRY #3191

What is the difference between crystalline and amorphous solids?

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CHEMISTRY #3192

Silicon dioxide (SiO₂) has a giant covalent structure. Why is it not an electrical conductor?

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CHEMISTRY #3193

Why is graphene considered a revolutionary material for electronics?

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CHEMISTRY #3197

Describe dot-and-cross diagram for phosphorus trichloride (PCl₃).

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CHEMISTRY #3204

Why is diamond transparent while graphite is opaque?

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CHEMISTRY #3205

The energy difference between valence and conduction bands in a solid is called the .

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CHEMISTRY #3206

Explain the difference between conductors, semiconductors, and insulators in terms of band theory.

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CHEMISTRY #3208

Adding controlled impurities to a semiconductor to change its conductivity is called __________.

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CHEMISTRY #3209

A material that conducts electricity with zero resistance is called a __________.

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CHEMISTRY #3032

Boron: B-10 (10.01 amu) and B-11 (11.01 amu). Average atomic mass = 10.81 amu. Calculate percentage abundance of each.

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CHEMISTRY #3053

What are isobars? Give an example.

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CHEMISTRY #3054

What are isotones? Give an example.

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CHEMISTRY #3064

Nitrogen atom has 7 protons. To achieve neon configuration, what charge would a nitrogen ion have?

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CHEMISTRY #3065

A mass spectrum shows peaks at m/z = 69 and 71 with heights in ratio 1:1. What is the element and its isotopes?

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CHEMISTRY #3066

What is the basic principle of mass spectrometry for determining isotopic masses?

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CHEMISTRY #3071

An element has two isotopes: isotope X (mass 10.01 amu, 20%) and isotope Y (mass unknown, 80%). Relative atomic mass is 10.81. Calculate mass of isotope Y.

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CHEMISTRY #3074

Write the electronic configuration of iron (atomic number 26).

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CHEMISTRY #3075

Write the electronic configuration of bromine (atomic number 35).

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CHEMISTRY #3087

Isobars have the same number but different numbers.

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CHEMISTRY #3088

Isotones have the same number of __________.

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CHEMISTRY #3091

An ion X²⁺ has 18 electrons. What is element X?

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CHEMISTRY #3093

Uranium-235 is used in nuclear reactors while uranium-238 is not. What is the main difference between these isotopes?

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CHEMISTRY #3094

What is heavy water (D₂O) and how does its composition differ from ordinary water?

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CHEMISTRY #3095

Explain why the first ionization energy of sodium is lower than that of magnesium.

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CHEMISTRY #3096

Explain why the atomic radius of chlorine is smaller than that of sulfur.

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Completed

CHEMISTRY #3097

Why does chlorine gas (Cl₂) show peaks at m/z = 70, 72, and 74 in a mass spectrometer?

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Completed

CHEMISTRY #3098

Bromine has two isotopes: Br-79 (50.7%) and Br-81 (49.3%). Predict the mass spectrum pattern for Br₂.

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CHEMISTRY #3099

Chromium (atomic number 24) has electron configuration [Ar] 4s¹ 3d⁵, not [Ar] 4s² 3d⁴. Explain why.

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CHEMISTRY #3100

Cobalt-60 is a gamma emitter; cobalt-59 is stable. What is the medical use of cobalt-60?

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CHEMISTRY #3101

Iodine-131 is used to treat thyroid disorders. Why is iodine-131 suitable rather than a different isotope of another element?

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CHEMISTRY #3103

Argon-40 is used in potassium-argon dating of rocks. What is the source of Ar-40 in rocks?

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CHEMISTRY #3104

Which is larger: Na⁺ or F⁻? Explain why.

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CHEMISTRY #3106

What happens to the size of a nitrogen atom when it becomes N³⁻?

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CHEMISTRY #3118

When carbon-14 decays, what element does it become?

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CHEMISTRY #2844

Explain why iron nails in contact with a piece of zinc do not rust, but iron nails in contact with copper rust more quickly.

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CHEMISTRY #2851

Explain how galvanizing protects iron even when the zinc coating is scratched.

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CHEMISTRY #2869

If 10 g of magnesium is completely burned in oxygen, calculate mass of MgO produced. (Mg=24, O=16)

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CHEMISTRY #2871

Compare and contrast rusting of iron with combustion of magnesium. Similarities and differences?

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CHEMISTRY #2872

Design guidelines for the public to reduce personal contribution to air pollution. Include five practical tips.

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CHEMISTRY #2873

Explain link between fossil fuel combustion, acid rain, and damage to limestone buildings. Write equations.

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CHEMISTRY #2874

A steel bridge in coastal area needs rust prevention. Suggest best method(s) with justification.

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CHEMISTRY #2875

The Montreal Protocol banned CFCs. Why was this successful? How did chemistry help?

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CHEMISTRY #2876

Student used gas syringe with heated copper. Initial volume 50.0 cm³, final 39.5 cm³. a) Calculate % O₂ b) Why might value be lower than 21%? c) What remains?

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CHEMISTRY #2882

How is sulfur dioxide removed from power plant emissions?

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CHEMISTRY #2906

How are nitrogen oxides (NOx) formed in car engines?

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CHEMISTRY #2908

What is buffering capacity of a lake?

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CHEMISTRY #2911

What does an electrostatic precipitator do?

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CHEMISTRY #2912

What does a wet scrubber remove from exhaust gases?

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CHEMISTRY #2913

What historical event caused temporary global cooling?

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CHEMISTRY #2915

Soot from incomplete combustion, which absorbs sunlight and warms the atmosphere, is called .

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CHEMISTRY #2916

How do scientists measure ancient temperatures using ice cores?

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CHEMISTRY #2776

A student is given a black powder mixture of sulfur, iron filings, and salt. Design a step-by-step procedure to separate all three components.

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CHEMISTRY #2777

Explain, using kinetic theory, what happens to the particles when an ice cube melts and then the resulting water boils to become steam.

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CHEMISTRY #2778

Compare simple and fractional distillation. Include mixture type, apparatus, and principle.

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CHEMISTRY #2779

Is burning a candle a physical or chemical change? Justify by describing wax melting vs wick burning.

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CHEMISTRY #2780

Why must pharmaceutical companies produce pure drugs? How can chromatography check drug purity?

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CHEMISTRY #2796

What is the difference between adsorption and absorption?

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CHEMISTRY #2797

What happens if the wrong solvent is used in paper chromatography?

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CHEMISTRY #2814

What is efflorescence?

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CHEMISTRY #2815

What is deliquescence?

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CHEMISTRY #2819

A substance that absorbs enough water from the air to form a solution is __________.

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CHEMISTRY #2820

A hydrated salt that loses water of crystallization to the air is __________.

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CHEMISTRY #2630

If you accidentally break a mercury thermometer in the lab, why is it important to follow special cleanup procedures (using sulfur powder) and not just sweep it up?

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CHEMISTRY #2646

A student is given a mixture containing iron filings, sand, salt, and small plastic beads. Design a complete separation plan to isolate each component, explaining the principle used at each step.

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CHEMISTRY #2647

"Chemistry is both a blessing and a curse." Discuss this statement with reference to drugs, plastics, and fertilizers.

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CHEMISTRY #2648

Compare and contrast the structure and use of a beaker, a conical flask, and a measuring cylinder. Why can't a beaker be used for precise volume measurement?

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CHEMISTRY #2650

Explain the connection between the development of new materials (like lightweight alloys or polymers) by chemists and the fuel efficiency of modern cars or airplanes.

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CHEMISTRY #2717

Name two principles of green chemistry.

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CHEMISTRY #2719

What is addition polymerization?

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Completed

CHEMISTRY #2720

What is condensation polymerization?

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CHEMISTRY #2727

What product is formed when ethanol is heated with concentrated sulfuric acid (dehydration)?

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PHYSICS #2534

What is the depletion layer? How is it formed?

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PHYSICS #2541

Explain why the conductivity of a semiconductor increases with temperature while that of a metal decreases.

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PHYSICS #2545

In an n-type semiconductor, why are electrons called majority carriers even though the material is electrically neutral?

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PHYSICS #2546

Calculate the number of holes in an n-type silicon sample with donor concentration 10¹⁶ cm⁻³. (Given nᵢ for silicon = 1.5 × 10¹⁰ cm⁻³)

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PHYSICS #2547

Explain the formation of the depletion layer at a p-n junction.

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PHYSICS #2549

Sketch the I-V characteristic of a silicon diode, labeling forward/reverse regions, knee voltage, and breakdown region.

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PHYSICS #2551

A diode has reverse saturation current of 1 μA at room temperature. What current flows when forward-biased at 0.6 V? (Assume n=1, e/(kT) ≈ 40 V⁻¹)

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PHYSICS #2553

Why does the reverse current in a diode increase dramatically at breakdown?

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PHYSICS #2562

A center-tapped full-wave rectifier uses a transformer with 24-0-24 V RMS secondary. Calculate: a) Peak voltage across each half-secondary b) Average DC output voltage c) PIV across each diode

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PHYSICS #2563

A bridge rectifier is connected to a 24 V RMS secondary (no center tap). Calculate: a) Peak voltage b) Average DC output voltage c) PIV across each diode

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PHYSICS #2564

Compare the PIV requirements for center-tapped and bridge rectifiers giving the same DC output voltage.

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PHYSICS #2567

A full-wave rectifier with a 1000 μF smoothing capacitor supplies a load current of 500 mA. The mains frequency is 50 Hz. Estimate the ripple voltage.

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PHYSICS #2569

Explain why the output voltage of an unregulated power supply decreases as the load current increases.

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PHYSICS #2570

What is a Zener diode? How is it used for voltage regulation?

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PHYSICS #2571

Half-wave rectifier with 10:1 step-down transformer from 230 V, 50 Hz, load 100 Ω. Calculate: a) Peak secondary voltage b) Average load voltage and current c) Power dissipated d) Ripple frequency

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PHYSICS #2572

Repeat previous for full-wave bridge rectifier with same transformer and load.

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PHYSICS #2573

Bridge rectifier with 2200 μF capacitor, 200 mA load, 50 Hz, 12 V RMS secondary. Calculate ripple voltage and approximate DC output.

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PHYSICS #2574

Design a power supply for 12 V DC at 1 A from 230 V, 50 Hz. Specify: a) Turns ratio b) Rectifier type c) Capacitor for 1 V ripple d) Diode ratings

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PHYSICS #2575

Explain why the voltage drop across a conducting silicon diode is approximately 0.7 V. How does this affect rectifier output?

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Completed

PHYSICS #2576

A student builds a half-wave rectifier and measures 15 V DC output. With a large capacitor added, voltage rises to 22 V. Explain.

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PHYSICS #2595

A __________ diode acts as a voltage-controlled capacitor.

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PHYSICS #2596

A __________ diode has a lower forward voltage drop (0.2-0.4 V) and faster switching than silicon diodes.

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PHYSICS #2597

The maximum theoretical efficiency of a half-wave rectifier is about __________%.

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PHYSICS #2598

What is Transformer Utilization Factor (TUF)?

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PHYSICS #2600

The ripple factor for a half-wave rectifier (without filter) is approximately:

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PHYSICS #2601

The ripple factor for a full-wave rectifier (without filter) is approximately:

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PHYSICS #2605

In silicon, __________ mobility is higher than hole mobility.

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PHYSICS #2607

The ideal diode equation is I = Iₛ(__________).

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PHYSICS #2609

What is the difference between avalanche breakdown and Zener breakdown?

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PHYSICS #2446

What are the requirements for a good medical tracer?

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PHYSICS #2448

What is the difference between low-level and high-level radioactive waste?

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PHYSICS #2452

Which type of radiation is most dangerous outside the body? Which is most dangerous inside the body? Explain.

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PHYSICS #2455

Why is plastic or aluminum used to shield beta radiation rather than lead?

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PHYSICS #2461

Write the nuclear equation for the beta-minus decay of Strontium-90.

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PHYSICS #2466

Identify the missing particle: ¹⁴₇N + n → ¹⁴₆C + ?

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PHYSICS #2467

Write the equation for the beta-plus decay of Carbon-11.

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PHYSICS #2471

A sample contains 2.4 × 10²⁰ atoms of a radioactive isotope. After 12 years, 3.0 × 10¹⁹ atoms remain. Calculate the half-life.

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PHYSICS #2472

The activity of a source falls from 800 Bq to 50 Bq in 12 days. Find the half-life.

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PHYSICS #2477

Explain the principle of carbon dating. Why can't it be used for rocks millions of years old?

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PHYSICS #2479

Why is technetium-99m (half-life 6 hours) a good medical tracer? Why better than a 10-year half-life isotope?

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PHYSICS #2480

Describe how a radioactive tracer is used to study kidney function.

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PHYSICS #2481

How does a smoke detector use radioactivity? Why is an alpha emitter suitable?

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PHYSICS #2483

What are the advantages and disadvantages of using radiation to treat cancer?

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PHYSICS #2488

What is the difference between low-level and high-level radioactive waste? Give examples.

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PHYSICS #2489

Describe one method for disposing of high-level radioactive waste.

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Completed

PHYSICS #2491

A sample contains two radioactive isotopes: A (half-life 4 days) and B (half-life 8 days). Initially, A activity = 800 Bq, B = 400 Bq. Calculate: a) Total activity after 8 days b) Time when activities equal

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PHYSICS #2492

Uranium-238 decays to stable lead-206. Half-life 4.5×10⁹ years. Rock sample has 0.8 g U-238 and 0.2 g Pb-206. Assuming all Pb from U decay, estimate age.

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PHYSICS #2493

Patient injected with 10 mL of ¹³¹I (200 MBq/mL). Thyroid takes up 20%. Thyroid mass 20 g. Each decay deposits 0.5 MeV. Calculate dose in grays.

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PHYSICS #2494

Plutonium-239 has half-life 24,000 years. How many years for 99.9% to decay?

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PHYSICS #2495

Derive the relationship N = N₀e^{-λt} where λ is decay constant. Show λ = ln2/T½.

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PHYSICS #2496

Explain why beta particles have a continuous energy spectrum while alpha particles have discrete energies.

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PHYSICS #2514

The average annual background radiation dose to a person is about __________ mSv.

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PHYSICS #2519

What isotope is commonly used in PET (Positron Emission Tomography) scans?

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PHYSICS #2520

What is the Bragg peak in proton therapy for cancer?

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PHYSICS #2522

A sample contains 1×10¹⁵ atoms of an isotope with half-life 10 days. Calculate initial activity in Bq.

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PHYSICS #2524

What is specific activity?

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PHYSICS #2359

Why does the photoelectric effect provide evidence for the particle nature of light?

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PHYSICS #2367

How many photons per second are emitted by a 10 mW laser operating at 600 nm?

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PHYSICS #2371

Calculate the maximum speed of photoelectrons emitted from a metal with work function 2.5 eV when illuminated by light of wavelength 400 nm. (mₑ = 9.1 × 10⁻³¹ kg)

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PHYSICS #2376

In a photoelectric experiment, data given: f(10¹⁴ Hz): 5.0,6.0,7.0,8.0 and Vₛ(V): 0.2,0.6,1.0,1.4. Plot graph and determine Planck's constant, work function, threshold frequency.

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PHYSICS #2378

From a photoelectric experiment, the threshold frequency for a metal is found to be 5.5 × 10¹⁴ Hz. Calculate the work function. If light of frequency 7.5 × 10¹⁴ Hz is used, what stopping potential is needed?

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PHYSICS #2379

Explain why the graph of photocurrent against intensity is a straight line through the origin for frequencies above threshold.

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PHYSICS #2382

How many 100 W solar panels (each producing 100 W under full sun) are needed to power a house requiring 5 kW average power? Assume 5 hours of full sun equivalent per day.

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PHYSICS #2384

Why are photocells for visible light made with cathodes coated with low work function materials like cesium?

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PHYSICS #2386

Light of wavelength 200 nm falls on a metal surface. The stopping potential is 2.5 V. Calculate: a) Work function in eV b) Threshold wavelength c) Maximum speed of electrons d) Stopping potential if wavelength halved

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PHYSICS #2387

When light of wavelength 400 nm is incident on a metal, KE_max=1.0 eV. When wavelength is 300 nm, KE_max=2.5 eV. Calculate Planck's constant and work function.

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PHYSICS #2388

A beam of light with power 5 mW and wavelength 500 nm falls on a photocell. If 1% of the incident photons eject electrons, calculate the photocurrent.

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PHYSICS #2389

Prove that the slope of the Vₛ vs f graph is h/e and the intercept is -Φ/e.

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PHYSICS #2390

In a photoelectric experiment, the maximum kinetic energy of photoelectrons is plotted against frequency. The graph is a straight line with slope 6.6 × 10⁻³⁴ J s/Hz. What does this slope represent? If the intercept on the energy axis is -2.5 eV, find the work function and threshold frequency.

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PHYSICS #2391

A metal has work function 2.0 eV. What is the longest wavelength that can eject electrons? If light of wavelength 400 nm is used, what stopping potential is needed? If the intensity is doubled, what happens to the stopping potential and the photocurrent?

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PHYSICS #2392

Explain why the photoelectric effect cannot be explained by wave theory but is explained by photon theory.

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PHYSICS #2408

A 100 W light bulb emits 5% of its power as 500 nm light. How many photons per second are emitted?

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PHYSICS #2412

Light of 350 nm gives stopping potential 1.5 V. Find threshold wavelength.

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PHYSICS #2416

An LED emits 10 mW of light at 600 nm from an electrical input of 50 mW. How many photons per second are emitted? What is the efficiency?

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PHYSICS #2418

A 100 W sodium lamp emits yellow light at 589 nm with 30% efficiency. How many photons per second are emitted?

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PHYSICS #2423

A __________ tube uses the photoelectric effect and secondary emission to greatly amplify weak light signals.

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PHYSICS #2424

The __________ of a photocell is the fraction of incident photons that produce an electron.

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PHYSICS #2426

What are the three main predictions of Einstein's photon theory of the photoelectric effect?

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PHYSICS #2428

How does the photovoltaic effect differ from the photoelectric effect?

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PHYSICS #2430

The minimum photon energy that can be absorbed by a solar cell is determined by its __________ gap.

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PHYSICS #2431

List the key experimental observations of the photoelectric effect that classical wave theory could not explain.

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PHYSICS #2433

What did Millikan's photoelectric experiments verify?

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PHYSICS #2434

The photoelectric effect was first systematically studied experimentally by __________.

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PHYSICS #2435

The photoelectric effect was first observed accidentally by __________ in 1887.

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PHYSICS #2263

Describe the main parts of a Coolidge X-ray tube.

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PHYSICS #2266

Why is the anode often made to rotate?

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PHYSICS #2268

What is the purpose of the beryllium window in an X-ray tube?

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PHYSICS #2270

What is meant by "bremsstrahlung" radiation?

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PHYSICS #2271

What are characteristic X-rays?

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PHYSICS #2284

Explain how increasing the accelerating voltage affects the X-ray beam.

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PHYSICS #2285

Why is it important to cool the anode in an X-ray tube? How is cooling achieved?

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PHYSICS #2286

What is the difference between the continuous X-ray spectrum and characteristic X-ray lines?

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PHYSICS #2293

What is the approximate voltage required to produce X-rays with minimum wavelength 0.02 nm?

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PHYSICS #2294

Mammography uses soft X-rays (around 20-30 kV). Why are hard X-rays not used for this application?

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PHYSICS #2295

Industrial radiography of thick steel plates uses hard X-rays (hundreds of kV). Why?

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PHYSICS #2297

How would you show that X-rays can ionize air?

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PHYSICS #2299

What evidence proves that X-rays are electromagnetic waves?

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PHYSICS #2300

A beam of X-rays has intensity I₀. After passing through 2 mm of aluminum, its intensity is reduced to I₀/4. Calculate the linear attenuation coefficient μ of aluminum for these X-rays.

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PHYSICS #2303

Explain the difference between stochastic and deterministic effects of radiation.

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PHYSICS #2304

Why are rapidly dividing cells (like in bone marrow) more sensitive to X-rays?

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PHYSICS #2306

Calculate the thickness of lead required to reduce the intensity of an X-ray beam to 1/1000 of its original value if the half-value layer is 0.5 mm.

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PHYSICS #2310

A certain concrete has a half-value layer of 50 mm for 100 kV X-rays. What thickness is equivalent to 2 mm of lead (HVL for lead = 0.5 mm) for the same X-rays?

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PHYSICS #2311

X-ray tube: 80 kV, 25 mA, tungsten (Z=74), efficiency 1%. Calculate: a) Power input b) X-ray power output c) Heat power d) Photons/s if average photon energy 40 keV

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PHYSICS #2312

The intensity of an X-ray beam is reduced to 20% of its original value after passing through 3 mm of lead. Calculate the half-value layer for lead at this energy.

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PHYSICS #2313

In an X-ray diffraction experiment, X-rays of wavelength 0.154 nm are incident on a crystal with interplanar spacing 0.28 nm. Calculate the angle at which the first-order maximum occurs using Bragg's law: nλ = 2d sinθ.

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PHYSICS #2315

Compare the minimum wavelength produced in an X-ray tube when the voltage is 50 kV and when it is 100 kV. What is the ratio of the minimum wavelengths? What is the ratio of the maximum photon energies?

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PHYSICS #2316

Explain why X-ray tubes have a beryllium window rather than a glass window.

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PHYSICS #2317

A radiographer accidentally leaves a hand in the primary X-ray beam for 10 seconds. The beam intensity at that point is 2 mW/cm². The area exposed is 5 cm². Calculate the total energy deposited. If the mass of tissue exposed is 50 g, estimate the absorbed dose in grays.

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PHYSICS #2338

The minimum wavelength from an X-ray tube is 0.008 nm. Calculate the accelerating voltage.

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PHYSICS #2341

Explain how a sodium iodide (NaI) scintillation detector detects X-rays.

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PHYSICS #2343

What is Compton scattering and why is it important in X-ray imaging?

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PHYSICS #2344

What is the photoelectric effect and why is it dominant in diagnostic X-ray imaging?

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PHYSICS #2347

What are the key features of a continuous X-ray spectrum from a tungsten target?

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PHYSICS #2348

What factors affect X-ray image quality?

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PHYSICS #2349

Why do X-ray tubes need to be "warmed up" before use?

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PHYSICS #2350

What is a typical rotating anode speed and why is high speed beneficial?

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PHYSICS #2108

State two advantages of a ring main circuit.

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PHYSICS #2112

What is an RCD (Residual Current Device) and how does it protect against electric shock?

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PHYSICS #2118

Using the same 100 MW at 25 kV, line resistance 10 Ω. Calculate power loss and percentage loss.

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PHYSICS #2120

Same power and line resistance (10 Ω), current 250 A. Calculate power loss and percentage loss.

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PHYSICS #2121

Line carries 500 A at 132 kV, resistance 15 Ω. Find power transmitted and power loss.

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PHYSICS #2122

300 km line, resistance 0.08 Ω/km, current 600 A. Find total R and power loss.

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PHYSICS #2124

Power station transmits 200 MW. Line resistance 20 Ω. Find loss at 200 kV and 400 kV.

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PHYSICS #2126

TV rated 120 W, 230 V, protected by 3 A fuse. Is this appropriate?

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PHYSICS #2131

Why are some appliances double insulated and have no earth wire?

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PHYSICS #2133

Why is the earth pin in a UK plug longer than the live and neutral pins?

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PHYSICS #2137

10 LED bulbs (10 W each) for 5 h, 2 kW kettle for 0.5 h, 150 W TV for 4 h, 1.5 kW AC for 3 h. Tariff 28p/kWh. Find total cost.

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PHYSICS #2143

8.5 kW shower used 15 min/day. Tariff 30p/kWh. Find daily energy and annual cost.

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PHYSICS #2144

Line resistance 0.5 Ω/km, 200 km long, carries 800 A at 400 kV. Find total R, power loss, transmitted power, percentage loss.

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PHYSICS #2145

Same power (320 MW) at 200 kV (half voltage). Find new current and loss.

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PHYSICS #2146

10×60W lamps (0.6 kW) 5 h/day, 2 kW heater 2 h/day, fridge 0.15 kW × 24×0.3, washing machine 1.2 kW × 1.5 h × 2 days/week. Tariff 28p/kWh. Find weekly cost.

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PHYSICS #2147

Power station 11 kV to 275 kV. Primary turns 200. Find secondary turns and current at 150 MW.

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PHYSICS #2148

Ring main with 30 A breaker, cable rated 20 A. Is this safe? Explain.

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PHYSICS #2149

A 100 W, 230 V lamp is fitted with a 13 A fuse. Explain why this is dangerous.

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PHYSICS #2150

RCD trips at 30 mA imbalance. Person touches live wire, 50 mA flows to earth. What happens?

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PHYSICS #2152

100 W incandescent vs 12 W LED, both 4 h/day, 365 days, 30p/kWh. Find annual cost and saving.

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PHYSICS #2170

Overhead transmission lines are usually made of __________ because it is a good conductor and lightweight.

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PHYSICS #2173

In a ring main, the cable rating is typically A, protected by a A circuit breaker.

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PHYSICS #2177

Modern grid transformers have efficiencies exceeding __________%.

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PHYSICS #2178

__________ stations pump water uphill to store energy and release it as electricity when needed.

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PHYSICS #2183

What conditions are necessary for producing cathode rays?

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PHYSICS #2184

Name the four main parts of an electron gun.

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PHYSICS #2187

How is the focus of the beam adjusted?

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PHYSICS #2189

Describe an experiment to show that cathode rays travel in straight lines.

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PHYSICS #2190

Describe an experiment to show that cathode rays are negatively charged.

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PHYSICS #2199

Why is electric deflection used in CROs rather than magnetic deflection?

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PHYSICS #2202

Same electron (E_k = 4.0×10⁻¹⁶ J, m=9.1×10⁻³¹ kg). Calculate speed.

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PHYSICS #2205

Same CRO (I=0.2 mA). Calculate number of electrons striking screen per second.

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PHYSICS #2206

If accelerating voltage is doubled, what happens to electron speed?

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PHYSICS #2208

If accelerating voltage is doubled, what happens to deflection sensitivity (deflection per volt on Y-plates)?

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PHYSICS #2210

What is the shape of an electron's path in a uniform electric field between parallel plates?

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PHYSICS #2211

What rule determines the direction of deflection of an electron beam in a magnetic field?

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PHYSICS #2212

An electron beam enters an electric field directed upward. Which way does it deflect?

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PHYSICS #2213

An electron beam moves horizontally to the right. A magnetic field is directed into the page. Which way does it deflect?

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PHYSICS #2214

Compare electric and magnetic deflection of cathode rays. Give one advantage of each.

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PHYSICS #2215

A CRO shows 2 cm deflection for a certain Y-plate voltage. If accelerating voltage is doubled, what is the new deflection for the same Y-plate voltage?

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PHYSICS #2219

Same waveform, find RMS voltage.

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PHYSICS #2226

Time base = 10 μs/div, 2.5 cycles over 10 divisions. Find frequency.

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PHYSICS #2227

3 cycles in 6 divisions, time base = 5 ms/div. Find frequency.

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PHYSICS #2228

Distance between peaks = 4.2 cm, time base = 2 ms/cm. Find frequency.

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PHYSICS #2229

500 Hz signal, time base = 0.5 ms/div, screen width = 10 divisions. How many complete cycles visible?

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PHYSICS #2230

Y-gain=2 V/div, time base=1 ms/div. P-P height=3.2 div, one cycle=2.5 div. Find V_peak, V_rms, T, f.

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PHYSICS #2231

Triangular wave: P-P=4.8 div, Y-gain=0.5 V/div, T=8 ms. Find V_peak and f.

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PHYSICS #2232

Y-gain=1 V/div, waveform height=6 div P-P, time base=0.2 ms/div, one cycle=5 div. Find V_rms and f.

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PHYSICS #2233

Sine wave: peak=4 V, f=1 kHz. Screen has 8 divisions vertically, 10 divisions horizontally. What Y-gain and time base?

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PHYSICS #2234

V_accel=2000 V, plate separation d=1 cm, plate length l=2 cm, screen distance L=20 cm. Find deflection sensitivity (cm/V). Use formula D = (e E l L)/(m v² d)? Actually deflection D = (V_d * L * l)/(2 * d * V_accel).

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PHYSICS #2235

Electron beam undeflected: E=3×10⁴ N/C, B=0.02 T. Find speed.

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PHYSICS #2236

Same electrons (v=1.5×10⁶ m/s) in B=0.02 T. Find radius of curvature.

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PHYSICS #2237

Ellipse: Y-intercept ±2 div, Y-max ±4 div. Find phase difference.

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PHYSICS #2238

Beam current 100 μA, V_accel=10 kV. Find beam power. If 80% heats screen, find rate of temp rise for screen mass 2 g, c=0.5 J/g°C.

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PHYSICS #2239

Why does the trace become fainter when the time base speed is increased?

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PHYSICS #2240

CRO shows V_pp=16.97 V, multimeter reads 6.0 V. What waveform is it?

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PHYSICS #2245

The and anodes accelerate and focus the electron beam.

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PHYSICS #2256

In electric deflection, the electron path is __________ between the plates.

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PHYSICS #2006

What does the negative sign in Faraday's Law (E = -N dΦ/dt) indicate?

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PHYSICS #2013

Wing length 30 m, B=5×10⁻⁵ T, speed 200 m/s, motion perpendicular. Find e.m.f. between wingtips.

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PHYSICS #2014

Coil area 0.01 m², 500 turns, B=0.1 T, rotates 90° in 0.05 s. Find average e.m.f.

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PHYSICS #2015

50 turns, flux changes from 0.02 Wb to -0.02 Wb in 0.01 s. Find induced e.m.f.

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PHYSICS #2016

North pole of magnet moved towards a coil. What is the direction of induced current as seen from the magnet side?

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PHYSICS #2017

South pole of magnet moved away from a coil. What is direction of induced current as seen from magnet side?

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PHYSICS #2020

A metal ring placed above an electromagnet jumps up when current is switched on. Explain using Lenz's Law.

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PHYSICS #2021

A bar magnet dropped through a hollow copper tube falls more slowly than through air. Why?

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PHYSICS #2023

What is the function of slip rings in an AC generator?

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PHYSICS #2024

What is the function of a split-ring commutator in a DC generator?

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PHYSICS #2025

Why is the e.m.f. from an AC generator sinusoidal?

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PHYSICS #2026

Coil area 0.03 m², 200 turns, rotates at 3000 rpm in B=0.2 T. Find peak e.m.f.

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PHYSICS #2027

A DC generator produces a pulsating output. How is this made smoother in practice?

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PHYSICS #2035

List four causes of energy loss in a transformer.

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PHYSICS #2036

Why is the core of a transformer laminated?

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PHYSICS #2037

What is the purpose of using a soft iron core in a transformer?

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PHYSICS #2039

Step-down transformer: 240 V primary, 6 V secondary, lamp 12 W. Find turns ratio and primary current.

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PHYSICS #2041

Primary 800 turns, secondary 40 turns, primary 240 V, secondary current 5 A. Find secondary voltage and primary current.

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PHYSICS #2042

Efficiency 95%, primary 230 V, 1.5 A, secondary 115 V. Find secondary current.

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PHYSICS #2043

Power station: 25 kV stepped up to 400 kV. Primary 1000 turns. Find secondary turns.

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PHYSICS #2044

Transformer to match 4 Ω load to 100 Ω source. Find turns ratio.

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PHYSICS #2045

Primary 200 turns, secondary 1200 turns, primary current 10 A. Find secondary current and identify transformer type.

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PHYSICS #2046

Coil R=5 Ω, L=0.2 H connected to 12 V DC. Find final current. If switched off and current falls to zero in 0.01 s, find average induced e.m.f.

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PHYSICS #2047

Rectangular coil 100 turns, 0.1×0.2 m, rotates at 600 rpm in B=0.5 T. Find peak e.m.f. and max current if load is 10 Ω.

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PHYSICS #2048

Transformer: primary 240 V, 2 A; secondary 110 V, 10 A. Find efficiency and power loss.

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PHYSICS #2050

Coil 50 turns, area 0.01 m², B=0.3 T, field reduced to zero in 0.1 s, R=2 Ω. Find e.m.f. and charge flow.

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PHYSICS #2055

The negative sign in Faraday's Law represents __________.

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PHYSICS #2068

Hysteresis loss is caused by the __________ and demagnetization of the core each cycle.

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PHYSICS #2069

Flux leakage occurs when some magnetic flux does not __________ both coils.

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PHYSICS #2071

The peak e.m.f. of an AC generator is given by E₀ = __________.

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PHYSICS #2072

Induction cooktops use electromagnetic induction to heat the __________ directly.

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PHYSICS #2073

A metal detector works on the principle of __________ induction.

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PHYSICS #2074

Eddy current brakes work because induced currents create a magnetic field that opposes the __________.

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PHYSICS #2076

An autotransformer has a __________ winding that serves as both primary and secondary.

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PHYSICS #2077

A current transformer is used to measure large __________ by stepping it down.

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PHYSICS #2078

A voltage transformer (potential transformer) is used to step down __________ for measurement.

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PHYSICS #2081

The phenomenon of inducing an e.m.f. in a coil due to a change in its own current is called __________ induction.

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PHYSICS #2084

In a motor, the rotating coil generates an induced e.m.f. that opposes the supply voltage, called __________ e.m.f.

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PHYSICS #2085

Maxwell added the displacement current term to complete the equations showing that __________ waves exist.

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PHYSICS #2086

The Faraday constant (F) is related to __________ and is used in electrolysis.

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PHYSICS #2087

Differential protection in transformers compares primary and secondary __________ to detect faults.

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PHYSICS #2088

Welding transformers have high current and low __________ outputs.

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PHYSICS #2090

The humming sound in transformers is caused by __________, the change in core dimensions with magnetic field.

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PHYSICS #2092

The core of a high-frequency transformer (like in switch-mode power supplies) is often made of __________ instead of iron.

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PHYSICS #2093

Nanocrystalline core materials like Nanoperm have very low __________ loss and high permeability.

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PHYSICS #2095

A tap changer is used to adjust the __________ ratio of a transformer while it is in service.

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PHYSICS #2096

Resonant transformers (Tesla coils) use resonance to achieve very high __________.

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PHYSICS #2097

The SI unit of flux linkage (NΦ) is the __________-turn (or weber-turn).

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PHYSICS #2098

Induction cooktops typically operate at frequencies of __________ kHz to produce eddy currents.

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PHYSICS #2099

The power rating of a transformer is expressed in __________ (volt-amperes) rather than watts.

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PHYSICS #2100

An ideal transformer assumes no losses, perfect coupling, and __________ permeability core.

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PHYSICS #1929

Why do microwave ovens use a frequency that is absorbed by water molecules?

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PHYSICS #1931

Why are microwaves suitable for satellite communication?

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PHYSICS #1932

What is the cosmic microwave background radiation?

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PHYSICS #1938

Explain how night vision goggles work.

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PHYSICS #1940

What is thermography? Give two applications.

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PHYSICS #1942

Explain how a rainbow is formed.

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PHYSICS #1943

How do fiber optics use visible light (or infrared) for communication?

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PHYSICS #1945

Why is UV-C the most dangerous type of UV?

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PHYSICS #1948

Explain how UV lamps are used to sterilize water.

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PHYSICS #1949

How do fluorescent lights work?

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PHYSICS #1954

Describe how X-rays are produced in an X-ray tube.

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PHYSICS #1956

Why do bones show up clearly on an X-ray image?

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PHYSICS #1957

What is a CT scan and how does it differ from a regular X-ray?

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PHYSICS #1960

How are gamma rays produced?

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PHYSICS #1961

What is the difference between X-rays and gamma rays in terms of their origin?

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PHYSICS #1963

Why is lead used to shield against X-rays and gamma rays?

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PHYSICS #1964

What is radiotherapy and how does it work?

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PHYSICS #1972

Mobile phone 900 MHz, power 2 W. Find photons per second. (h = 6.63×10⁻³⁴ J s)

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PHYSICS #1973

X-ray tube at 50 kV. Find minimum wavelength. (h=6.63×10⁻³⁴ J s, e=1.6×10⁻¹⁹ C, c=3×10⁸ m/s)

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PHYSICS #1974

Radar echo 0.12 ms. Find distance. f = 10 GHz. Find λ.

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PHYSICS #1975

Red light λ=700 nm, gamma λ=0.01 nm. How many times more energetic is gamma?

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PHYSICS #1976

Microwave oven 2.45 GHz, power 800 W. Find photons per second.

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PHYSICS #1995

The cosmic microwave background radiation is evidence for the __________.

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PHYSICS #1720

What are the rules of the New Cartesian Sign Convention for lenses?

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PHYSICS #1731

How is presbyopia different from hypermetropia?

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PHYSICS #1737

Object 50 cm from convex lens f=30 cm. Find image position and nature.

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PHYSICS #1738

Object 15 cm from convex lens f=10 cm. Find image position and magnification.

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PHYSICS #1739

Object 8 cm from convex lens f=12 cm. Find image position and nature.

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PHYSICS #1741

Virtual image at 30 cm from convex lens f=15 cm. Find object distance.

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PHYSICS #1742

Object 5 cm tall at 25 cm from convex lens f=15 cm. Find image position, size, nature.

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PHYSICS #1743

Object 2 cm tall, real image 4 cm tall, object distance 30 cm. Find focal length.

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PHYSICS #1744

Object 40 cm from concave lens f=20 cm. Find image position and magnification.

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PHYSICS #1745

Virtual image 10 cm from concave lens, object 20 cm. Find focal length.

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PHYSICS #1746

Object 4 cm tall at 30 cm from concave lens f=15 cm. Find image position and size.

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PHYSICS #1747

Convex lens f=20 cm, image at 30 cm. Find object positions for real and virtual images.

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PHYSICS #1748

Convex lens f=10 cm, magnification 3×. Find object distance for real and virtual images.

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PHYSICS #1752

Myopic person has far point 80 cm. Find lens focal length and power.

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PHYSICS #1753

Hypermetropic, near point 50 cm. Lens to read at 25 cm. Find focal length and power.

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PHYSICS #1754

Person uses lens power -1.5 D. What is far point?

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Completed

PHYSICS #1755

Person uses +2 D lens for near vision. Find near point without glasses.

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PHYSICS #1756

Hypermetropic near point 75 cm. Lens to read at 25 cm. Find power.

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Completed

PHYSICS #1757

Person cannot see beyond 1.2 m. Find lens power.

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PHYSICS #1763

Convex f=20 cm, concave f=10 cm in contact. Find power and focal length.

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PHYSICS #1764

Convex f=30 cm, concave f=20 cm in contact. Find f combination.

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PHYSICS #1765

Object and screen 60 cm apart. Lens moved 20 cm gives another image. Find f.

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PHYSICS #1785

A person with presbyopia has near point 80 cm. What power lens for reading at 25 cm?

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PHYSICS #1786

Microscope: fₒ=1.5 cm, fₑ=2.5 cm, object at 2.2 cm from objective. Final image at near point (25 cm). Find tube length and magnifying power.

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PHYSICS #1787

Telescope L=1.05 m, M=20. Find f₀ and fₑ.

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PHYSICS #1788

Beam converges to point P. Lens placed 15 cm from P. Convex lens f=20 cm. Where does light converge now?

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PHYSICS #1789

Same beam, concave lens f=-20 cm. Where does light converge now?

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PHYSICS #1790

Convex f=30 cm, concave f=20 cm in contact. Is combination converging or diverging?

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PHYSICS #1796

Astigmatism is corrected using a __________ lens.

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PHYSICS #1798

The tube length of a compound microscope is approximately the sum of and .

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PHYSICS #1641

What are the assumptions of Bernoulli's Principle?

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PHYSICS #1646

Why are two ships sailing parallel and close in the same direction sometimes drawn towards each other?

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PHYSICS #1648

How does an atomizer (perfume sprayer) work?

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PHYSICS #1650

What is the Magnus Effect?

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PHYSICS #1651

Where is turbulent flow desirable?

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PHYSICS #1653

How does a Venturi meter measure flow rate?

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PHYSICS #1656

Hose diameter 2 cm (A≈3.14×10⁻⁴ m²), v=1 m/s. Thumb reduces area to 0.2 cm² (2×10⁻⁵ m²). Find new speed.

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PHYSICS #1658

Main pipe radius 5 cm (A≈0.00785 m²), v=2 m/s. Splits into 5 pipes each radius 1 cm (A_each≈3.14×10⁻⁴ m²). Find v in each small pipe.

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PHYSICS #1661

Artery radius 2 mm (A₁=1.26×10⁻⁵ m²), v₁=0.2 m/s. Splits into 150 capillaries each r=0.05 mm (A_each=7.85×10⁻⁹ m²). Find v in capillaries.

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PHYSICS #1662

Horizontal pipe: Point A: P=100 kPa, v=2 m/s. Point B: v=5 m/s. Find P_B. (ρ=1000 kg/m³)

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PHYSICS #1663

Venturi: A₁=0.1 m², P₁=120 kPa, A₂=0.05 m², P₂=80 kPa, ρ=800 kg/m³. Find v₁.

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PHYSICS #1664

Air over wing v=250 m/s, under v=200 m/s, ρ=1.3 kg/m³. Find ΔP = P_bottom - P_top.

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PHYSICS #1666

Horizontal pipe: P₁=150 kPa, v₁=1 m/s. P₂=100 kPa. Find v₂. (ρ=1000 kg/m³)

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PHYSICS #1667

Pipe narrows: D₁=20 cm (r=0.1m, A₁=0.0314 m²), v₁=1 m/s, P₁=200 kPa. D₂=5 cm (r=0.025m, A₂=0.00196 m²). Find v₂ and P₂.

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PHYSICS #1669

Same tank, hole area 1 cm² = 10⁻⁴ m². Find volume flow rate.

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PHYSICS #1670

Why does the exit velocity decrease as the tank empties?

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PHYSICS #1671

Is Bernoulli's principle alone sufficient to explain airplane lift?

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PHYSICS #1672

How are the continuity equation and Bernoulli's principle linked mathematically?

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PHYSICS #1690

The sum P + ½ρv² + ρgh is called __________ pressure.

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PHYSICS #1691

How does a carburettor work in an engine?

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PHYSICS #1694

How does a fast bowler make a cricket ball swing (curve in air)?

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PHYSICS #1695

Why do golf balls have dimples?

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PHYSICS #1696

What is a pitot tube used for?

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PHYSICS #1698

The mushroom cloud from an explosion is partly due to:

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PHYSICS #1699

What does the Reynolds number determine?

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PHYSICS #1570

What are the three conditions necessary for total internal reflection to occur?

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PHYSICS #1575

How is a mirage formed on a hot road?

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PHYSICS #1577

Why is cladding necessary in an optical fibre?

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PHYSICS #1578

Why are prisms often preferred over mirrors in high-quality optical instruments?

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PHYSICS #1579

Why do stars twinkle, but planets do not?

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PHYSICS #1580

A fish underwater sees the world above through a "circle of light". What determines the angle of this circle?

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PHYSICS #1581

Why does a diamond sparkle more than a piece of glass cut to the same shape?

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PHYSICS #1585

Light from water (n=4/3) to air at i=30°. Calculate r in air.

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PHYSICS #1590

Medium X to Y: i=35°, r=20°. Which is denser and what is n of Y relative to X?

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PHYSICS #1592

Light inside glass (n=1.5) at i=35°. Will it emerge?

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PHYSICS #1593

For the same glass (n=1.5, i=35°), calculate angle of refraction in air.

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PHYSICS #1598

Glass n=1.5, i=50° inside glass. Does TIR occur?

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PHYSICS #1599

Liquid n=1.7, i=40° inside liquid to air. What happens?

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PHYSICS #1600

Medium n=1.8. Find critical angle.

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PHYSICS #1601

Same medium, i=20°. Find r in air.

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PHYSICS #1602

Same medium, i=40°. What happens?

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PHYSICS #1603

Glass prism n=1.52, ray inside strikes hypotenuse at 45°. Will TIR occur?

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PHYSICS #1604

Water 10 cm (n=1.33) plus oil 4 cm (n=1.45). Find total apparent depth.

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PHYSICS #1605

Glass 6 cm (n=1.5) over coin, water 8 cm (n=4/3) above glass. Find total apparent depth.

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Completed

PHYSICS #1606

Fibre core n=1.6, cladding n=1.48. Find critical angle at core-cladding interface.

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Completed

PHYSICS #1607

For the same fibre, find maximum acceptance angle in air (n_air=1).

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PHYSICS #1608

The formula apparent depth = real depth / n is derived using which approximation?

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PHYSICS #1616

A mirage is caused by and of light in layers of air at different temperatures.

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PHYSICS #1621

A right-angled prism can deviate light by 90° using TIR when light enters the prism __________.

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PHYSICS #1623

The circular window through which a fish sees the outside world is called __________.

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PHYSICS #1627

Which phenomena are involved in rainbow formation?

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PHYSICS #1629

How does refractive index vary with wavelength?

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PHYSICS #1499

Two masses: 2 kg and 3 kg over a frictionless pulley. g=10 m/s². Find acceleration.

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PHYSICS #1500

Same system, find tension in the string.

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PHYSICS #1520

2 kg ball dropped from 5 m (v=10 m/s down), rebounds to 3.2 m (v=8 m/s up). Find Δp (up positive).

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PHYSICS #1521

Same ball, find impulse imparted to the ball.

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PHYSICS #1522

Same ball, contact time 0.02 s. Find average force from floor on ball.

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Completed

PHYSICS #1523

Rocket mass 5000 kg, burns fuel 50 kg/s, exhaust speed 2000 m/s. Find thrust.

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Completed

PHYSICS #1524

Same rocket, find initial acceleration (g=10 m/s²).

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Completed

PHYSICS #1531

4 kg at 5 m/s collides with 2 kg at 3 m/s same direction. After, 4 kg moves at 4 m/s. Find velocity of 2 kg.

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Completed

PHYSICS #1532

5 kg at 6 m/s collides head-on with 3 kg at -4 m/s and sticks. Find common velocity.

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PHYSICS #1533

Uranium (238 u) emits alpha (4 u) at 1.5×10⁷ m/s. Find recoil of daughter (234 u).

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PHYSICS #1535

20 g bullet into stationary 980 g block. Block rises 5 cm after impact. Find velocity after impact.

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PHYSICS #1536

Same system, find initial velocity of bullet.

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PHYSICS #1537

2000 kg truck at 10 m/s hits stationary 1000 kg car. Truck moves at 6 m/s after. Find car velocity.

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PHYSICS #1538

Same collision, find impulse experienced by the car.

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PHYSICS #1539

3 kg at 4 m/s collides with stationary 2 kg. After, 3 kg at 1.5 m/s. Find 2 kg velocity and determine if elastic.

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PHYSICS #1551

In an elastic collision between two equal masses with one initially stationary, what happens?

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PHYSICS #1552

The impulse-momentum theorem is derived from which of Newton's Laws?

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PHYSICS #1554

A stationary 6 kg object explodes into two fragments of 2 kg and 4 kg. If the 2 kg fragment moves at 8 m/s, find velocity of 4 kg fragment.

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PHYSICS #1555

In a collision between two cars, which experiences the greater change in momentum?

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PHYSICS #1557

Water flows at 10 kg/s and hits a wall at 15 m/s, stopping. Find force on wall.

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PHYSICS #1427

Why would someone use a lever with a mechanical advantage of 0.5?

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PHYSICS #1428

Why is the velocity ratio always greater than the mechanical advantage in real machines?

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PHYSICS #1442

Pump lifts 200 kg water per minute from 15 m deep. g=10 m/s². Find power.

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Completed

PHYSICS #1457

Same wheel: efficiency 75%. Find actual load.

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Completed

PHYSICS #1465

Machine VR=5, efficiency 70%, load 1400 N. Find effort.

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PHYSICS #1471

5 kg block, frictionless incline height 3 m, length 5 m. Find acceleration.

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PHYSICS #1473

Same block, find time to reach bottom (s=5 m, a=6 m/s²).

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PHYSICS #1475

Same ball, find PE and KE at half max height (5.625 m).

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Completed

PHYSICS #1476

Car 1200 kg, slope 1:5, driving force 4000 N, friction 600 N. Find net force up.

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PHYSICS #1477

Same car, find acceleration.

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Completed

PHYSICS #1478

Same car, find power when moving at 15 m/s.

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Completed

PHYSICS #1479

4 pulleys (VR=4), efficiency 75%, load 600 N lifted 3 m. Find effort.

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Completed

PHYSICS #1480

Same system: effort distance = 3 × 4 = 12 m. Find work input and output.

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PHYSICS #1338

Why is the total resistance of a parallel combination less than the smallest individual resistance?

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PHYSICS #1339

Why is it dangerous to connect an ammeter in parallel across a battery?

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PHYSICS #1341

Two identical lamps in series to a battery. How does their brightness compare to a single lamp on the same battery?

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PHYSICS #1346

5 Ω, 10 Ω, 15 Ω in parallel. Find total resistance.

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Completed

PHYSICS #1350

4 Ω, 6 Ω, 12 Ω resistors. How to connect to get 2 Ω?

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Completed

PHYSICS #1351

Parallel branches: 10 Ω and 15 Ω. Total current = 5 A. Find current in each.

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Completed

PHYSICS #1357

Cell ε=1.5 V, R=4 Ω, I=0.3 A. Find internal r.

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Completed

PHYSICS #1358

Case 1: R=5 Ω, I=0.4 A. Case 2: R=2 Ω, I=0.7 A. Find ε and r.

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Completed

PHYSICS #1364

Two cells: each ε=2 V, r=0.5 Ω, in parallel to R=2.75 Ω. Find total ε and r.

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Completed

PHYSICS #1365

Same circuit, find current.

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Completed

PHYSICS #1374

Same motor, find efficiency.

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Completed

PHYSICS #1377

Same heater, find time to heat water.

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Completed

PHYSICS #1380

Why might the actual power differ from calculation?

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PHYSICS #1383

Same circuit, find current through 6 Ω resistor.

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PHYSICS #1384

Same circuit, find current through 3 Ω resistor.

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PHYSICS #1386

Same circuit, find power dissipated in internal resistance.

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Completed

PHYSICS #1387

For a cell with ε=12 V, r=2 Ω, what external resistance gives maximum power transfer?

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PHYSICS #1388

Same cell, find the maximum power transferred to the load.

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PHYSICS #1400

Maximum power transfer from a cell occurs when external resistance R equals the __________ resistance.

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PHYSICS #1257

Why do waves approaching a beach become nearly parallel to the shore?

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PHYSICS #1262

What conditions are necessary for two wave sources to produce a stable interference pattern?

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PHYSICS #1263

Explain why a soap bubble shows colours.

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PHYSICS #1275

From y = A sin(ωt - kx), how can you determine the direction of wave travel?

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PHYSICS #1280

What is the difference in harmonic series between open and closed pipes?

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PHYSICS #1281

Why are there "hot spots" and "cold spots" in a microwave oven?

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PHYSICS #1286

Light λ = 600 nm through single slit width 0.1 mm. Will significant diffraction occur?

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PHYSICS #1287

Slits 0.5 mm apart, screen 2 m away, λ = 500 nm. Calculate fringe spacing.

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PHYSICS #1288

Two waves, path difference 0.3 m, λ = 0.6 m. Constructive or destructive?

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PHYSICS #1297

y = 0.02 sin(2πx) cos(100πt). Find antinode amplitude.

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PHYSICS #1298

From y = 0.02 sin(2πx) cos(100πt). Find wavelength.

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PHYSICS #1299

From same equation, find frequency.

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PHYSICS #1300

From same equation, find speed of constituent waves.

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PHYSICS #1308

ω = 314 rad/s, k = 2 rad/m. Find wave speed.

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PHYSICS #1309

Wave speed 20 m/s, f = 10 Hz, A = 0.05 m. Write equation (travel +x).

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PHYSICS #1311

f = 50 Hz, v = 300 m/s, Δx = 1.5 m. Find phase difference.

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PHYSICS #1312

y = 0.03 sin(200πt - 4πx). Find y at x=0.25 m, t=0.01 s.

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PHYSICS #1313

Same equation, find phase difference between points 0.5 m apart.

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PHYSICS #1314

λ=500 nm, d=0.2 mm, D=1.5 m. Find fringe spacing.

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PHYSICS #1315

Same setup, find position of 5th bright fringe from centre.

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PHYSICS #1316

Same setup, find position of 3rd dark fringe from centre.

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PHYSICS #1317

String length 1.2 m, fixed both ends, 3rd harmonic frequency 100 Hz. Find wavelength.

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PHYSICS #1318

Same string (λ=0.8 m, f=100 Hz). Find wave speed.

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PHYSICS #1319

Closed pipe length 0.5 m, resonances at 170 Hz and 510 Hz. Find speed of sound.

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PHYSICS #1320

y₁ = 0.05 sin(100πt - 2πx), y₂ = 0.05 sin(100πt + 2πx). Find stationary wave equation.

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PHYSICS #1193

Why do electric field lines never cross?

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PHYSICS #1197

Why does a neutral point exist midway between two equal like charges?

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PHYSICS #1215

Why is connecting a capacitor directly across a battery dangerous?

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PHYSICS #1220

Why is the charge on each capacitor the same in a series circuit?

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PHYSICS #1225

Electron (q = -1.6×10⁻¹⁹ C) in E field 2000 N/C downward. Find force magnitude and direction.

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PHYSICS #1230

Capacitance C. Area doubled, separation doubled. New capacitance in terms of C.

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PHYSICS #1231

Capacitor stores 0.02 J at 100 V. Find capacitance.

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PHYSICS #1233

Find total C for 2 μF, 3 μF, 5 μF in series.

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PHYSICS #1236

10 μF in series with (20 μF parallel 30 μF). Find total C.

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PHYSICS #1237

(2 μF parallel 4 μF) in series with 3 μF. Find total C.

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PHYSICS #1238

(8 μF series 24 μF) in parallel with 6 μF. Find total C.

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PHYSICS #1239

10 μF and unknown C in series give 4 μF. Find unknown C.

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PHYSICS #1242

Area 0.2 m², separation 2 mm, air, charged to 200 V. Find C, Q, E, and field strength.

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PHYSICS #1243

Same capacitor disconnected, plates pulled to 4 mm. Find new C, V, E, energy.

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PHYSICS #1244

Capacitor C charged to V connected to uncharged 2C. Find final voltage.

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PHYSICS #1245

For the previous problem, find energy lost.

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PHYSICS #1246

4 μF and 6 μF in series across 100 V. Find total C, charge, and voltages.

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PHYSICS #1140

Why is a 13 A fuse dangerous in a lamp that normally draws 0.5 A?

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PHYSICS #1141

Why does a fuse blow faster when a short circuit occurs compared to a slow overload?

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PHYSICS #1147

Why is the earth pin longer than the live and neutral pins in a plug?

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PHYSICS #1149

An appliance works but the brown and blue wires are swapped. Why is this dangerous?

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PHYSICS #1151

How does an RCD provide additional safety beyond a fuse?

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PHYSICS #1160

Wire resistance 5 Ω, 1000 J heat in 4 seconds. Find current.

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PHYSICS #1169

Extension lead rated 13 A. 2 kW heater + 1 kW kettle simultaneously on 230 V. Safe?

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PHYSICS #1170

3 kW immersion heater heats 50 kg water from 15°C to 60°C (c=4200). Energy needed?

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PHYSICS #1171

Same heater. Time to heat water (100% efficiency).

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PHYSICS #1174

10 kW power transmitted at 230 V over 5 km each way (cable 0.1 Ω/km). Power loss?

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PHYSICS #1175

Same 10 kW transmitted at 11,000 V. Power loss?

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PHYSICS #1177

100 W lamp and 2 kW heater in parallel on 230 V, protected by 13 A fuse. Will it blow?

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PHYSICS #1180

Same appliances for 2 hours. Energy in kWh and cost at $0.15/kWh.

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PHYSICS #1087

Why must we account for the heat absorbed by the calorimeter itself?

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PHYSICS #1092

Why does ice at 0°C feel colder than water at 0°C?

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PHYSICS #1097

If a student forgets to account for the calorimeter's heat capacity, will calculated specific heat be too high or too low?

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PHYSICS #1104

2 kg (c=800) at 80°C mixed with 3 kg unknown at 20°C. Final T=35°C. Find c of unknown.

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PHYSICS #1107

Heat to convert 0.5 kg ice at -5°C to water at 30°C. (c_ice=2100, c_w=4200, L_f=334,000)

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PHYSICS #1108

Heat to convert 0.2 kg water at 20°C to steam at 100°C. (c_w=4200, L_v=2,260,000)

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PHYSICS #1109

Heat released when 0.1 kg steam at 100°C condenses and cools to 40°C. (c_w=4200, L_v=2,260,000)

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PHYSICS #1110

Heat removed to convert 0.5 kg water at 20°C to ice at -5°C. (c_w=4200, c_ice=2100, L_f=334,000)

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PHYSICS #1111

Al calorimeter (0.1 kg, c=900) with 0.2 kg water at 20°C. 0.3 kg metal at 100°C added. Final T=25°C. Find c of metal.

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PHYSICS #1112

Cu calorimeter (0.05 kg, c=390) with 0.15 kg water at 18°C. 0.08 kg metal at 95°C added. Final T=22°C. Find c of metal.

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PHYSICS #1113

Al calorimeter (0.2 kg, c=900) with 0.3 kg water at 25°C. Dry ice at 0°C added. Final mass=0.55 kg, T=10°C. Find L_f of ice.

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PHYSICS #1114

Cu calorimeter (0.1 kg, c=390) with 0.2 kg water at 30°C. Steam at 100°C added. Final T=40°C. Final mass=0.305 kg. Find L_v.

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PHYSICS #1115

Al calorimeter (0.1 kg, c=900) with 0.2 kg liquid at 20°C. Cu block (0.15 kg, c=390) at 100°C added. Final T=25°C. Find c of liquid.

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PHYSICS #1116

50 g ice at 0°C into 200 g water at 30°C in 100 g Al calorimeter (c=900). Find final T. (c_w=4200, L_f=334,000)

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PHYSICS #1117

Steam at 100°C into 500 g water at 20°C in 200 g Cu calorimeter (c=390) to reach 50°C. Find mass steam needed. (L_v=2.26×10⁶, c_w=4200)

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PHYSICS #1118

500 W heater heats 1 kg water from 20°C to 100°C. Time taken? (c_w=4200)

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PHYSICS #1119

Same 500 W heater, time to vaporize all water at 100°C? (L_v=2.26×10⁶)

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PHYSICS #1120

2 kW kettle with 1.5 kg water at 15°C. Time to boil? (c_w=4200)

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PHYSICS #1121

Same 2 kW kettle, time to boil away half the water (0.75 kg) once boiling? (L_v=2.26×10⁶)

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PHYSICS #1028

How does a graph of volume against temperature (in °C) for a gas provide evidence for absolute zero?

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PHYSICS #1029

Two gas samples have same volume, pressure, and temperature. One is helium, one is oxygen. Do they contain the same number of molecules?

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PHYSICS #1034

A gas has volume 300 mL at 0°C. Temperature to double volume at constant pressure?

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PHYSICS #1036

Car tyre at 220 kPa, 15°C rises to 250 kPa. New temperature in °C?

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PHYSICS #1038

Gas: 500 cm³ at 27°C, 100 kPa. Volume at 127°C, 200 kPa?

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PHYSICS #1039

Gas: 2.0 L at 20°C, 1.0 atm. Volume at 100°C, 1.5 atm?

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PHYSICS #1040

Gas at 0°C, 1.0 atm, 10.0 L. Pressure to compress to 5.0 L at 100°C?

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PHYSICS #1041

Gas: 300 cm³ at 27°C, 750 mm Hg. Volume at STP (0°C, 760 mm Hg)?

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PHYSICS #1042

Balloon: 100 m³ at 100 kPa, 27°C. Volume at 20 kPa, -23°C?

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PHYSICS #1043

Gas: 400 cm³ at 27°C, 80 kPa reduced to 300 cm³ at 120 kPa. New temperature in °C?

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PHYSICS #1044

Calculate volume of 3 moles at 27°C and 2.02 × 10⁵ Pa. (R = 8.314 J/mol·K)

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PHYSICS #1045

How many moles in 10.0 L at 20°C and 1.5 atm? (1 atm = 1.01×10⁵ Pa, R=8.314)

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PHYSICS #1046

Gas: P=200 kPa, V=5.0 L, T=27°C. Find number of moles. (R=8.314)

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PHYSICS #1047

Mass of O₂ (32 g/mol) in 20 L at 27°C and 1.5×10⁶ Pa. (R=8.314)

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PHYSICS #1048

0.5 moles in 12 L at 1.2×10⁵ Pa. Find temperature in °C. (R=8.314)

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PHYSICS #1049

Bubble from 20 m depth: bottom T=7°C, surface T=27°C, P_atm=100 kPa, ρ=1000 kg/m³, g=10. Find volume ratio V_surface/V_bottom.

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PHYSICS #1050

Flask at 27°C, 100 kPa heated to 127°C, seal broken then cooled to 27°C. Final pressure?

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PHYSICS #1051

20 L cylinder N₂ at 20°C, 15×10⁵ Pa. Pressure drops to 10×10⁵ Pa at same T. Mass used? (N₂=28 g/mol)

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PHYSICS #1052

Two equal volume flasks connected, gas at P₁,T₁ and P₂,T₂. Final pressure at uniform T?

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PHYSICS #1053

For an ideal gas, how is density related to pressure and temperature?

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PHYSICS #961

What shape is the velocity-time graph for a ball thrown upwards and returning? (Upwards positive)

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PHYSICS #962

How would you use a ticker-timer to find acceleration of a trolley?

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PHYSICS #963

What does the area under an acceleration-time graph represent?

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PHYSICS #970

First 10-dot interval = 5 cm, later 10-dot interval = 15 cm. Time between centres = 0.5 s. Find a.

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PHYSICS #979

Car accelerates from 5 m/s to 25 m/s over 100 m. Find acceleration.

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PHYSICS #980

For the same car, find time taken.

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PHYSICS #981

Particle: rest, a=4 m/s² for 5 s, then constant v for 10 s, then decelerates to rest in 2 s. Find max velocity.

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PHYSICS #982

For the same motion, find total distance.

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PHYSICS #983

Ball thrown down from 40 m with u=5 m/s (g=10 m/s²). Find impact velocity.

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PHYSICS #984

Stone A thrown up at 20 m/s, Stone B dropped 1 s later from same point (g=10 m/s²). When do they meet?

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PHYSICS #985

A body covers 10 m in 2nd second and 20 m in 4th second. Find initial velocity.

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PHYSICS #986

For the same body, find acceleration.

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PHYSICS #987

Car accelerates from rest to v, then continues at v for half the acceleration distance. Total time = 30 s. Find v.

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PHYSICS #988

The equations of motion can be derived from which graph?

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PHYSICS #1000

The area under an acceleration-time graph gives __________.

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PHYSICS #899

What is the direction of magnetic field lines inside a bar magnet?

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PHYSICS #900

What is the domain theory of magnetism?

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PHYSICS #903

Why does heating a magnet demagnetize it?

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PHYSICS #904

How does hammering demagnetize a magnet?

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PHYSICS #905

How can you demagnetize a magnet using AC?

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PHYSICS #910

What is a magnetic keeper?

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PHYSICS #912

What is magnetic declination?

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PHYSICS #913

What is the angle of dip (magnetic inclination)?

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PHYSICS #915

What would happen to a compass at the geographic North Pole?

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PHYSICS #916

Why does a soft iron nail become a temporary magnet near a magnet?

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PHYSICS #917

Using domain theory, how does stroking magnetize a steel bar?

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PHYSICS #919

A plotting compass is placed near the north pole of a bar magnet. Which way does it point?

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PHYSICS #920

Why are horseshoe magnet poles often connected by a soft iron keeper?

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PHYSICS #925

How can you test if a material is hard or soft magnetic?

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PHYSICS #926

An iron nail is stroked 20 times with the north pole of a magnet. What is the polarity at the end where strokes ended?

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PHYSICS #927

How can you reverse the polarity of a magnetized steel rod using a coil?

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PHYSICS #928

Why does hammering a magnet in an east-west direction demagnetize it more than in north-south?

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PHYSICS #929

How might some birds navigate using Earth's magnetic field?

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PHYSICS #930

Why is Earth's magnetic field thought to be generated in the core?

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PHYSICS #931

At which point is a compass needle parallel to a bar magnet?

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PHYSICS #938

The method of storing a horseshoe magnet with a soft iron piece uses a __________.

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PHYSICS #939

The Earth's magnetic north pole is actually a __________ pole.

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PHYSICS #871

Vernier caliper has zero error +0.03 cm. Observed reading = 2.45 cm. Find correct length.

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PHYSICS #872

Micrometer has zero error -0.02 mm. Observed reading = 5.78 mm. Find correct reading.

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PHYSICS #873

Vernier caliper: main scale 2.3 cm, vernier coincidence 7, LC=0.01 cm, zero error -0.02 cm. Find correct reading.

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PHYSICS #874

Micrometer: main scale 3.5 mm, thimble 25, zero error +0.03 mm. Find actual reading.

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PHYSICS #880

Add: 2.34 cm + 1.2 cm + 0.456 cm. Answer with correct sig figs.

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PHYSICS #881

Multiply: 3.2 cm × 4.56 cm. Answer with correct sig figs.

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PHYSICS #884

Convert 0.05 µs to seconds.

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PHYSICS #889

50 sheets total thickness = 8.5 mm (micrometer zero error -0.01 mm). Find thickness of one sheet in mm.

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PHYSICS #890

Micrometer: main scale 2.5 mm, thimble 32, zero error -0.03 mm. Find actual diameter in metres (standard form).

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PHYSICS #831

A cone on its base is stable, on its tip unstable, on its side neutral. Why?

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PHYSICS #835

Why do weightlifters bend their legs and keep their back straight when lifting?

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PHYSICS #836

A child's weighted toy figure always returns upright when pushed. How?

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PHYSICS #838

A uniform block has height 80 cm and base width 30 cm. Calculate the maximum angle before toppling.

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PHYSICS #839

A rectangular block of height 1.0 m and base width 0.4 m. Find the toppling angle.

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PHYSICS #840

A cylinder of diameter 20 cm and height 50 cm stands on its base. Will it topple at 25°? (CoG at centre)

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PHYSICS #841

A block of weight 100 N has base length 0.6 m and height 1.2 m. A horizontal force is applied at the top edge. Find minimum force to topple.

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PHYSICS #842

A vehicle has track width 1.8 m and CoG height 0.6 m. Calculate max slope angle before toppling sideways.

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PHYSICS #779

Why is it impossible to obtain a real image from a convex mirror?

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PHYSICS #782

In Cartesian sign convention, what is the sign of object distance (u)?

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PHYSICS #783

What is the sign of focal length (f) for a concave mirror using Cartesian convention?

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PHYSICS #784

What is the sign of focal length (f) for a convex mirror using Cartesian convention?

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PHYSICS #785

In Cartesian sign convention, what is the sign of v for a real image?

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PHYSICS #786

In Cartesian sign convention, what is the sign of v for a virtual image?

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PHYSICS #787

An object is placed 20 cm in front of a concave mirror of focal length 15 cm. Find the image distance using sign convention (u = -20, f = -15).

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PHYSICS #788

For the previous problem (u = -20, f = -15, v = -60), calculate the magnification.

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PHYSICS #789

An object is placed 25 cm from a concave mirror and a real image is formed 50 cm from the mirror. Find the focal length (u = -25, v = -50).

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PHYSICS #790

A convex mirror has focal length 30 cm. An object is placed 60 cm in front of it. Find image distance. (f = +30, u = -60)

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PHYSICS #792

An object 5 cm tall is placed 40 cm in front of a concave mirror of focal length 20 cm. Find image position. (u = -40, f = -20)

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PHYSICS #793

For the previous problem, calculate the image height.

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PHYSICS #794

A concave mirror forms a real image twice the size of the object. Object distance is 30 cm. Find image distance and focal length.

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PHYSICS #795

An object is placed 15 cm in front of a convex mirror. The image is formed 5 cm behind the mirror. Find focal length. (u = -15, v = +5)

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PHYSICS #796

A convex mirror in a car has focal length 2 m. A vehicle is 4 m behind the car. Find image distance. (f = +2, u = -4)

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PHYSICS #798

An object 2 cm high is placed 10 cm in front of a concave mirror. A real image 4 cm high is formed. Find image distance and focal length.

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PHYSICS #799

An object is placed 20 cm from a concave mirror. The image is three times the size of the object. Find the possible focal lengths.

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PHYSICS #800

A concave mirror of focal length 18 cm forms an image of an object placed at 12 cm. Find magnification. (u = -12, f = -18)

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PHYSICS #801

A convex mirror has radius of curvature 40 cm. An object is placed 30 cm in front. Find image distance. (R = 40 → f = 20, u = -30)

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PHYSICS #802

Prove that for a convex mirror, the image is always virtual, diminished, and between P and F.

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PHYSICS #803

Two mirrors (concave f=15, convex f=15) face each other 50 cm apart. Object 20 cm in front of concave. Find final image position.

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PHYSICS #809

According to the Cartesian sign convention, object distance u is always __________.

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PHYSICS #718

Why does a current-carrying conductor experience a force when placed in a magnetic field?

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PHYSICS #723

What makes the hammer in an electric bell strike the gong repeatedly?

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PHYSICS #724

How does a telephone earpiece work?

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PHYSICS #726

What is the function of the split-ring commutator in a DC motor?

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PHYSICS #730

Why is the magnetic field inside a solenoid uniform and strong?

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PHYSICS #731

A current-carrying conductor is placed between the poles of a magnet. If current flows from north to south (relative to field), what direction is the force?

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PHYSICS #734

Why is soft iron used for the core of an electromagnet in a bell and motor rather than steel?

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PHYSICS #735

What would happen if the contact screw were removed from an electric bell?

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PHYSICS #736

Why might a simple DC motor not start if the coil is exactly vertical?

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PHYSICS #738

Two parallel conductors carrying current in the same direction experience what force?

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PHYSICS #739

Two parallel conductors carrying current in opposite directions experience what force?

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PHYSICS #745

A DC motor coil has 100 turns, each 5 cm × 4 cm, current 2 A, field 0.3 T. Calculate maximum torque.

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PHYSICS #747

Why is a laminated core used in transformers and motors rather than a solid metal core?

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PHYSICS #754

The split-ring commutator in a DC motor ensures that the current reverses every __________ rotation.

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PHYSICS #755

Soft iron is used in electromagnets because it is easily and .

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PHYSICS #633

A wave enters a shallow region and slows down. What happens to its wavelength?

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PHYSICS #654

Radar at 10 GHz, plane 60 km away. Time for pulse to return? (v = 3 × 10⁸ m/s)

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PHYSICS #657

12 waves in 4 seconds. Distance between 1st and 4th crest = 0.6 m. Find frequency.

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PHYSICS #658

Same data (1st to 4th crest = 0.6 m). 1st to 4th crest = 3λ. Find λ.

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PHYSICS #659

Same data (f=3 Hz, λ=0.2 m). Find speed.

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PHYSICS #660

String fixed at both ends, fundamental frequency 100 Hz, v=200 m/s. Find string length.

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PHYSICS #537

A uniform beam of weight 50 N and length 4 m is pivoted at one end and held horizontal by a vertical force at the other end. Calculate the force.

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PHYSICS #538

A light rod AB is 3 m long. Forces: 10 N down at A, 20 N down at B. Find resultant magnitude and position from A.

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PHYSICS #539

Two parallel forces: 8 N and 12 N act in opposite directions on a light rod 2 m apart. Find resultant force.

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PHYSICS #540

For the opposite forces (8 N and 12 N, 2 m apart), find position of resultant from the 8 N force.

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PHYSICS #542

A uniform plank weight 100 N, length 5 m, rests on supports at ends. A 200 N weight is placed 1 m from one end. Calculate force on support nearest the weight.

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PHYSICS #545

A uniform metre rule weight 1.5 N pivoted at 40 cm. A 2 N weight at 20 cm. Where must a 3 N weight be hung to balance?

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PHYSICS #546

A man uses a 1.5 m spanner with 200 N force at 30° to the spanner. Calculate the effective moment.

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PHYSICS #548

A uniform bridge weight 50,000 N, length 20 m, on two end pillars. A lorry weight 30,000 N parked 5 m from one end. Calculate force on pillar nearest the lorry.

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PHYSICS #549

Why is a ladder safer at a steeper angle?

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PHYSICS #550

A uniform see-saw weighs 100 N, pivot at centre. Children weigh 250 N and 300 N. Where should they sit to balance? (Length 4 m total)

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PHYSICS #562

Why do pliers have long handles and short jaws?

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PHYSICS #421

What is meant by "action at sharp points"?

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PHYSICS #427

How can you charge a metal sphere positively by induction using a negatively charged rod?

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PHYSICS #428

Why is it necessary to earth a conductor during charging by induction?

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PHYSICS #430

When testing the charge on an object, why is increased leaf divergence the only sure sign the test charge is similar?

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PHYSICS #432

Why is the top of a lightning conductor pointed and made of copper?

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PHYSICS #434

How is static electricity used in a photocopier?

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PHYSICS #437

A positively charged electroscope is brought near a rod. The leaf first falls then rises as the rod approaches. What is the rod's charge?

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PHYSICS #440

Why can a charged object attract a neutral conductor?

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PHYSICS #441

What if a lightning conductor's point were replaced with a large metal ball?

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PHYSICS #443

How can you demonstrate that charge concentrates at sharp points?

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PHYSICS #445

A negatively charged rod is brought near a neutral electroscope, cap earthed then rod removed. Final charge on electroscope?

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PHYSICS #299

During the day, wind blows from the sea to the land (sea breeze). Why?

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PHYSICS #312

Why does frost form on a car windscreen rather than on the road on a cold night?

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PHYSICS #314

What happens if the vacuum in a vacuum flask is lost (air leaks in)?

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PHYSICS #320

How can you show that a dull black surface is a better emitter of heat than a shiny surface?

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PHYSICS #322

How do double-glazed windows reduce heat loss from a house?

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PHYSICS #323

Why does filling cavity walls with foam insulation improve thermal insulation?

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PHYSICS #324

Why does a solar water heater have a glass cover over the black collector plate?

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PHYSICS #325

Why do spaceships in deep space have shiny silver exteriors?

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PHYSICS #326

Why does a concrete path feel hotter than grass on a sunny day?

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PHYSICS #328

Why do we see mirages on hot roads?

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PHYSICS #330

Why are central heating radiators placed under windows?

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PHYSICS #342

What is a "black body" in physics?

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PHYSICS #345

What geological phenomenon is driven by convection in the Earth's mantle?

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PHYSICS #346

What drives large-scale ocean currents?

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PHYSICS #348

Why is thermal paste applied between a computer CPU and its heat sink?

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PHYSICS #259

During the day, wind blows from the sea to the land (sea breeze). Why?

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PHYSICS #260

At night, wind blows from land to sea (land breeze). Why?

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PHYSICS #261

How does a vacuum flask (thermos) reduce heat transfer by conduction?

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PHYSICS #262

How does a vacuum flask reduce heat transfer by radiation?

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PHYSICS #273

What does Leslie's cube demonstrate?

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PHYSICS #278

Why are space suits shiny (reflective) on the outside?

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PHYSICS #279

How does a greenhouse stay warm?

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PHYSICS #281

Why are the cooling coils at the back of a refrigerator usually black?

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PHYSICS #290

In a vacuum flask, the __________ between the inner and outer walls prevents heat transfer by conduction and convection.

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PHYSICS #193

What is meant by anomalous expansion of water?

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PHYSICS #200

What is the purpose of Hope's apparatus?

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PHYSICS #203

A brass plate has a circular hole. When heated, what happens to the hole diameter?

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PHYSICS #205

A glass stopper is stuck in a glass bottle. Which part should you heat to remove it?

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PHYSICS #210

In Hope's apparatus, what happens to the top and bottom thermometers?

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PHYSICS #211

If water did not have anomalous expansion, how would life in cold countries be different?

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PHYSICS #220

A gas occupies 500 mL at 27°C. At what temperature (in °C) will volume be 600 mL? (Pressure constant)

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PHYSICS #222

Why is a bimetallic strip of brass (α = 0.000019/°C) and invar (α ≈ 0.000001/°C) useful in thermostats?

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PHYSICS #223

A glass bottle with a narrow neck is filled with water at 4°C and sealed. What happens when cooled to 0°C?

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PHYSICS #224

The same bottle at 4°C is heated to 20°C. What happens?

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PHYSICS #226

Why do gases expand much more than solids for the same temperature rise?

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PHYSICS #227

Railway sections are 25 m long at 15°C. Max temp = 45°C. Gap = 1.5 cm. α = 1.2×10⁻⁵/°C. Will rails buckle?

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PHYSICS #236

In Hope's apparatus, the bottom thermometer cools to __________ °C and then stops.

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PHYSICS #239

Why is steel used as reinforcement in concrete despite different expansion coefficients?

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PHYSICS #143

Why does a crystal of potassium manganate take a long time to colour an entire beaker of water?

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PHYSICS #160

Why does water rise in a narrow glass tube?

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PHYSICS #161

Why does mercury fall (form a concave depression) in a narrow glass tube?

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PHYSICS #169

Why is it impossible to perfectly seal a container of air?

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PHYSICS #172

What would happen if smoke particles were much larger (like fine dust) in the smoke cell?

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PHYSICS #173

Hydrogen (H₂, light) and CO₂ (heavy) are released at opposite ends of a tube. Which reaches the other end first?

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PHYSICS #174

What is the connection between Brownian motion and diffusion?

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PHYSICS #176

A narrow tube is dipped into water. Water rises 5 cm. What happens with mercury?

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PHYSICS #177

What happens if an even narrower tube is used for water?

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PHYSICS #092

How does a siphon work?

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PHYSICS #097

A nail is pushed into wood with a force of 40 N. The tip area is 0.5 mm². Calculate pressure in Pa. (1 mm² = 10⁻⁶ m²)

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PHYSICS #103

What depth of mercury (ρ = 13,600 kg/m³) produces the same pressure as 10 m of water?

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PHYSICS #104

A U-tube contains water. Another liquid in one arm gives column height 15 cm while water rises 12 cm in the other arm. Find density of liquid.

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PHYSICS #107

A hydraulic lift lifts 12,000 N. Large piston area = 0.6 m², small piston area = 0.02 m². Minimum force needed on small piston?

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PHYSICS #109

If a barometer reads 750 mm Hg, what height of water barometer? (ρ_Hg = 13,600 kg/m³, ρ_water = 1000 kg/m³)

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PHYSICS #115

Why would a small leak cause hydraulic brakes to fail?

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PHYSICS #116

Why can a siphon not work in a vacuum?

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PHYSICS #119

Hydraulic press: small piston diameter = 4 cm, large = 40 cm. Force on small = 100 N. Calculate small piston area.

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PHYSICS #120

Using the same press, what load is lifted by the large piston?

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PHYSICS #121

U-tube with mercury. Water poured into one arm drops mercury by 2 cm in that arm. Height of water column? (ρ_Hg = 13.6 g/cm³)

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PHYSICS #122

Tank: water depth 2 m, oil layer above (ρ = 800 kg/m³, depth 1 m). Calculate total pressure at bottom. (g = 10 N/kg, atmospheric = 1.0 × 10⁵ Pa)

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PHYSICS #125

What is a hydraulic ram pump used for?

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PHYSICS #071

50 cm³ of liquid A (density 0.8 g/cm³) is mixed with 50 cm³ of liquid B (density 1.2 g/cm³). Assuming no volume change, what is the density of the mixture?

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PHYSICS #072

A micrometer screw gauge reads 0.02 mm when fully closed (negative zero error). What is the correct reading if the instrument shows 3.50 mm?

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PHYSICS #041

A rectangular block has length 5 cm, width 4 cm, height 2 cm, and mass 80 g. Calculate its density in kg/m³.

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PHYSICS #055

On a vernier caliper, the main scale reads 2.3 cm and the 4th vernier division coincides. If least count is 0.01 cm, what is the reading?

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PHYSICS #018

A spring of original length 10 cm is stretched to a length of 15 cm by a force of 25 N. Calculate the spring constant in N/m.

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PHYSICS #020

A spring has an original length of 8 cm. When a 20 N weight is hung on it, its length becomes 12 cm. Calculate the spring constant.

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PHYSICS #027

A 2 kg mass is hung on a spring. The spring extends by 4 cm. An additional 3 kg mass is then added. What is the total extension now? (Assume elastic limit not exceeded, g = 10 N/kg)

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PHYSICS #028

A rocket has a weight of 50,000 N on Earth. During launch, the engines provide an upward thrust of 80,000 N. Air resistance is 5,000 N. Calculate the resultant force.

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PHYSICS #029

Two springs, Spring P (k = 100 N/m) and Spring Q (k = 250 N/m), are each stretched by a force of 20 N. Which spring stretches more and by how much?

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PHYSICS #030

A beam balance measures mass while a spring balance measures weight. Why?

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CHEMISTRY #3685

Write the equation for the reaction of chlorine with cold dilute sodium hydroxide.

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Completed

CHEMISTRY #3688

How is hydrogen chloride gas prepared in the laboratory? Write the equation.

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CHEMISTRY #3694

How is sodium hypochlorite (bleach) manufactured? Write the equation.

MEDIUM +30 XP 5 min

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CHEMISTRY #3696

Why is chlorine gas collected by upward displacement of air rather than over water?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3700

Describe a chemical test to distinguish between chlorine gas and hydrogen chloride gas.

MEDIUM +30 XP 5 min

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CHEMISTRY #3703

What would you observe if chlorine gas is bubbled through a solution of potassium bromide? Explain with equation.

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CHEMISTRY #3707

Chlorine reacts with cold dilute NaOH to form and .

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CHEMISTRY #3708

The bleaching action of chlorine is due to the formation of __________ acid.

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CHEMISTRY #3712

Sodium hypochlorite is manufactured by reacting chlorine with __________ sodium hydroxide.

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Completed

CHEMISTRY #3714

Write balanced equation for preparation of chlorine from MnO₂ and HCl.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3717

Write equation for reaction of chlorine with water.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3718

Write equation for preparation of hydrogen chloride from NaCl and H₂SO₄ at low temperature.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3720

Write simplified equation for reaction of sodium hypochlorite with water to give hypochlorous acid.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3721

Calculate mass of MnO₂ (M=87) needed to produce 7.1 g Cl₂ (M=71). MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3723

What mass of NaCl (M=58.5) needed to produce 36.5 g HCl? NaCl + H₂SO₄ → NaHSO₄ + HCl

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3724

Calculate mass of NaOCl (M=74.5) produced when 71 g Cl₂ reacts with excess cold dilute NaOH. Cl₂ + 2NaOH → NaCl + NaOCl + H₂O

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3732

What color is seen when chlorine water is added to potassium bromide solution with CCl₄?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3733

What color is seen when chlorine water is added to potassium iodide solution with CCl₄?

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Completed

CHEMISTRY #3740

Write the equation for the reaction of chlorine with iron.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3741

Write the equation for the reaction of chlorine with copper.

MEDIUM +30 XP 5 min

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CHEMISTRY #3745

How would you test for bromide ion in solution?

MEDIUM +30 XP 5 min

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CHEMISTRY #3746

How would you test for iodide ion in solution?

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CHEMISTRY #3762

Name the two main crystalline allotropes of sulphur. At what temperature does one transform into the other?

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CHEMISTRY #3763

How is sulphur dioxide prepared in the laboratory? Write the equation.

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CHEMISTRY #3766

What is the test for sulphur dioxide gas?

MEDIUM +30 XP 5 min

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CHEMISTRY #3772

Describe how you would prepare a sample of monoclinic sulphur in the laboratory.

MEDIUM +30 XP 5 min

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CHEMISTRY #3776

Why is excess oxygen used in the Contact Process? How does it affect yield and rate?

MEDIUM +30 XP 5 min

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CHEMISTRY #3778

Explain why concentrated sulphuric acid is a strong dehydrating agent, but dilute sulphuric acid is not.

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CHEMISTRY #3779

Why is sulphuric acid called the "king of chemicals"? Give three major industrial uses.

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CHEMISTRY #3784

SO₂ bleaches by , while chlorine bleaches by .

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3785

The catalyst used in the Contact Process is __________.

MEDIUM +30 XP 5 min

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CHEMISTRY #3791

Write equation for reaction of SO₂ with sodium hydroxide solution.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3809

What is the molecular shape of SO₃?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3813

What is the product when H₂S and SO₂ react?

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CHEMISTRY #3815

What are "sulphur flowers"?

MEDIUM +30 XP 5 min

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CHEMISTRY #3820

In the Contact Process, a pressure of about __________ atmosphere is used, even though higher pressure would increase yield.

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Completed

CHEMISTRY #3583

Sketch and label an energy level diagram for an exothermic reaction. Show reactants, products, activation energy, and ΔH.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3585

State Hess's Law in words.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3588

Define lattice energy and hydration energy.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3591

Explain, in terms of bond breaking and bond making, why some reactions are exothermic and others endothermic.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3595

Draw an energy level diagram for an endothermic reaction with and without a catalyst. Label all parts.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3600

Why is it important to specify standard states when using enthalpy data?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3606

Lattice energy is the enthalpy change when one mole of an ionic compound is formed from its __________ ions.

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Completed

CHEMISTRY #3608

For an ionic compound to dissolve endothermically, the lattice energy must be __________ than the hydration energy.

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CHEMISTRY #3610

Calculate ΔH for 2NO(g) + O₂(g) → 2NO₂(g) given ΔH°f NO = +90 kJ/mol, ΔH°f NO₂ = +34 kJ/mol.

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Completed

CHEMISTRY #3621

Why are mean bond energies used instead of exact bond energies for molecules with multiple bonds of same type?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3628

Calculate heat released when 1 g of methane (CH₄, M=16) is burned. ΔH°c CH₄ = -890 kJ/mol.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3631

A compound with a __________ (more negative/less negative) ΔH°f is more stable.

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CHEMISTRY #3633

How would you measure enthalpy of neutralization in the lab?

MEDIUM +30 XP 5 min

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CHEMISTRY #3639

Draw and explain how a catalyst affects the energy profile of a reaction.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3642

Estimate ΔH for H-H + Cl-Cl → 2H-Cl using bond energies: H-H=436, Cl-Cl=242, H-Cl=431 kJ/mol.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3646

Write a thermochemical equation for the combustion of methane including ΔH.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3656

Define enthalpy change of solution (ΔHsol).

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3659

First electron affinity of most non-metals is __________ (exothermic/endothermic).

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3661

Define enthalpy of sublimation (ΔHsub).

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3665

A 50 g metal sample absorbs 500 J and temperature rises 20°C. Calculate specific heat capacity.

MEDIUM +30 XP 5 min

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CHEMISTRY #3667

A coffee-cup calorimeter operates at constant __________ (pressure/volume).

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3668

A bomb calorimeter operates at constant __________ (pressure/volume).

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3670

How can Hess's Law be used to find ΔH for a reaction with unavailable data?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3560

Why do helium balloons deflate faster than air-filled balloons?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3561

Write the ideal gas equation. What does R represent?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3569

What volume of CO₂ at STP is produced from combustion of 1 mol CH₄? CH₄ + 2O₂ → CO₂ + 2H₂O

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3571

The average kinetic energy of gas molecules is proportional to __________ temperature.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3522

State Charles's law. Why must temperature be in Kelvin when using it?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3524

Define diffusion. State Graham's law of diffusion.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3528

Which gas diffuses faster, helium (He, M=4) or nitrogen (N₂, M=28)? By what factor?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3529

Explain, using kinetic theory, why pressure increases when volume decreases (Boyle's law).

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3533

Why does a hot air balloon rise? Explain using Charles's law.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3536

A gas cylinder contains gas at high pressure. Why is it dangerous to expose the cylinder to high temperatures?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3547

Gas has volume 5.0 L at 20°C and 1.0 atm. Volume at STP (0°C, 1.0 atm)?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3549

Calculate ratio of diffusion rates of CH₄ (M=16) and SO₂ (M=64).

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3558

Explain why pressure increases with temperature in sealed container using kinetic theory and gas law.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3452

Compare the structures of diamond and graphite.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3454

Why does graphite conduct electricity but diamond does not?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3466

Explain why diamond and graphite have such different physical properties despite being made of the same element.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3468

A student heats a green powder and it turns black, producing a gas that turns limewater milky. Identify the green powder and write equation.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3471

Describe an experiment to show that CO₂ is denser than air.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3474

Why is it dangerous to run a car engine in a closed garage?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3476

Explain why solid CO₂ (dry ice) is a better coolant for transporting food than ordinary ice.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3495

Calculate mass of calcium oxide (quicklime) produced when 100 g of CaCO₃ is heated strongly. Ca=40, C=12, O=16

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3497

In reaction 2CO + O₂ → 2CO₂, what volume of O₂ is needed to burn 50 cm³ of CO? (All volumes at same conditions)

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3503

Why is carbon (coke) used to extract iron from its ore, but cannot be used to extract aluminium?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3509

Carbon monoxide is a __________ oxide because it does not react with acids or bases.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3514

, , and __ are the main greenhouse gases.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3519

Why is CO₂ used in fire extinguishers?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3385

Write the half-equation for the reaction at the cathode during electrolysis of molten lead(II) bromide.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3386

Write the half-equation for the reaction at the anode during electrolysis of molten sodium chloride.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3388

Why is aluminium extracted by electrolysis rather than by reduction with carbon?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3389

In the electrolysis of concentrated sodium chloride solution (brine), what products are formed at the anode and cathode?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3392

A student sets up electrolysis of molten lead(II) bromide. Describe observations at anode and cathode.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3393

Predict the products of electrolysis for molten calcium chloride. Write half-equations.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3396

Describe how to electroplate a steel key with copper. Include electrolyte, anode, cathode.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3407

The electrolyte for copper purification is __________ solution.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3421

Describe set-up to copper-plate an iron nail. Include electrolyte, electrodes, half-equations.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3429

What is the mass change at the cathode during electrolysis of CuSO₄ with copper electrodes?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3430

What is the mass change at the anode during electrolysis of CuSO₄ with copper electrodes?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3432

One faraday is the charge of mole(s) of electrons, approximately coulombs.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3433

During electrolysis of molten Al₂O₃, aluminium is produced at the and oxygen at the .

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3444

The industrial production of chlorine and sodium hydroxide is called the - process.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3447

During copper refining, impurities such as gold and silver collect as beneath the anode.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3448

Copper and silver electrodes are called __________ electrodes because they participate in the reaction.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3449

Explain why solid aluminium oxide does not conduct electricity, but molten aluminium oxide does.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3450

The reverse of water electrolysis occurs in a __________ fuel cell, producing electricity.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3211

Define atomic radius. State and explain the trend in atomic radius across Period 3 from sodium to argon.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3215

Explain the general trend in first ionization energy across Period 3.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3217

Why does electronegativity increase across a period?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3220

Arrange in order of increasing atomic radius: Al, Si, Mg, Cl. Explain your order.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3236

Period 3 atomic radii (pm): Na(186), Mg(160), Al(143), Si(117), P(110), S(104), Cl(99). Explain the trend.

MEDIUM +30 XP 5 min

Start Challenge

Completed

CHEMISTRY #3237

Period 3 IE (kJ/mol): Na(496), Mg(738), Al(578), Si(787), P(1012), S(1000), Cl(1251), Ar(1520). Why is Na value so low?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3240

Why does Ar have the highest ionization energy in Period 3?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3244

Element X has high IE, high EN, small atomic radius. Is it metal or non-metal? Suggest group.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3247

Predict for Br (Period 4, Group VII) relative to Cl (Period 3, Group VII): a) atomic radius? b) IE? c) EN?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3252

What is shielding (screening) effect?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3255

Which element in Period 3 has the smallest atomic radius?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3256

Order Period 3 elements by metallic character (most to least).

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3263

What is an isoelectronic series?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3264

Why is cesium (Cs) the most reactive alkali metal?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3265

Why is fluorine (F) the most reactive non-metal?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3266

An element in Period 4, Group II (alkaline earth) – predict its relative atomic radius, IE, and EN compared to magnesium.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3269

Explain why the reaction of alkali metals with water becomes more vigorous from Li to Cs.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3271

Order Na, Mg, Al by increasing first ionization energy.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3281

State the modern periodic law.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3282

What are the s, p, d, f blocks of the periodic table based on?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3297

Define covalent radius.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3298

Define van der Waals radius.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3126

Describe the dot-and-cross diagram for methane (CH₄).

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3129

Explain why metals are malleable and ductile.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3135

A substance is solid, conducts electricity, and is malleable. What type of structure?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3138

Explain why solid NaCl does not conduct electricity, but NaCl solution in water does.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3140

Diamond and graphite are both carbon. Why do they have different properties?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3142

Describe dot-and-cross diagram for CaCl₂ showing outer electrons only.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3154

Graphite conducts electricity because it has __________ electrons.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3155

Describe the dot-and-cross diagram for magnesium oxide (MgO).

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3156

Describe the dot-and-cross diagram for calcium chloride (CaCl₂).

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3157

Describe the dot-and-cross diagram for water (H₂O).

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3162

Write the formula for the compound formed between magnesium and nitrogen.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3170

What is hydrogen bonding?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3171

Describe the bonding in ammonia (NH₃).

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3172

What is the shape of methane (CH₄) and why?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3173

What is a polar covalent bond?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3175

Define electronegativity.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3176

Hydrogen bonding is a strong type of __________ force.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3177

Water has high surface tension and high specific heat capacity due to __________.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3188

Compare ionic and covalent bonding: type of elements, electron behavior, melting point, conductivity.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3189

Why is diamond not used in pencils instead of graphite?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3194

Draw dot-and-cross diagram for NaCl (outer electrons only).

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3195

Draw dot-and-cross diagram for MgO (outer electrons only).

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3196

Describe dot-and-cross diagram for hydrogen sulfide (H₂S).

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3198

Name two substances with giant covalent structure other than diamond and graphite.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3201

Which are the weakest intermolecular forces?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3202

The weakest type of intermolecular force is called force.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3203

Forces between polar molecules are called - forces.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3207

Why is silicon used in computer chips?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3029

An ion has 12 protons, 10 electrons, and 12 neutrons. What is its: a) atomic number, b) mass number, c) charge, d) symbol?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3030

Chlorine: Cl-35 (34.97 amu, 75.77%) and Cl-37 (36.97 amu, 24.23%). Calculate relative atomic mass of chlorine.

MEDIUM +30 XP 5 min

Start Challenge

Completed

CHEMISTRY #3031

Copper: Cu-63 (62.93 amu, 69.17%) and Cu-65 (64.93 amu, 30.83%). Calculate relative atomic mass of copper.

MEDIUM +30 XP 5 min

Start Challenge

Completed

CHEMISTRY #3033

Magnesium: Mg-24 (78.6%), Mg-25 (10.1%), Mg-26 (11.3%). Calculate relative atomic mass.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3036

Atom has 19 protons, 20 neutrons, 19 electrons. Write: a) atomic number b) mass number c) electronic configuration d) group and period.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3037

Write electronic configuration of: a) Na⁺, b) Mg²⁺, c) Al³⁺, d) O²⁻, e) F⁻, f) Cl⁻. State noble gas achieved.

MEDIUM +30 XP 5 min

Start Challenge

Completed

CHEMISTRY #3043

Define relative atomic mass (Ar).

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3051

Write the electronic configuration of O²⁻ ion.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3052

Write the electronic configuration of Mg²⁺ ion.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3061

Aluminum atom has 13 protons and 13 electrons. If it loses 3 electrons, what is the charge and symbol of the ion?

MEDIUM +30 XP 5 min

Start Challenge

Completed

CHEMISTRY #3072

Lithium has two isotopes: Li-6 (6.015 amu, 7.5%) and Li-7 (7.016 amu, 92.5%). Calculate relative atomic mass.

MEDIUM +30 XP 5 min

Start Challenge

Completed

CHEMISTRY #3089

Explain why atoms are electrically neutral even though they contain charged particles.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3090

An element has electronic configuration 2,8,3. Determine its position in the Periodic Table and its valency.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3092

Why is carbon-14 useful for dating archaeological artifacts but carbon-12 is not?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3102

Why can't carbon-14 dating be used for dinosaur fossils (65+ million years old)?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3105

Is a Cl⁻ ion larger or smaller than a Cl atom? Explain.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3110

Neon has three isotopes: Ne-20 (90.5%), Ne-21 (0.3%), Ne-22 (9.2%). Which peak is tallest in mass spectrum?

MEDIUM +30 XP 5 min

Start Challenge

Completed

CHEMISTRY #3111

Calculate relative atomic mass of neon from abundances: Ne-20 (90.5%), Ne-21 (0.3%), Ne-22 (9.2%).

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3113

Write the electronic configuration of Al³⁺.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3116

Name the three isotopes of hydrogen and give their symbols.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3117

Carbon has three isotopes: C-12, C-13, C-14. Which is used for carbon dating and why?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3119

A wooden artifact has 25% of its original carbon-14. How many half-lives have passed?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #3120

Up to what age is carbon-14 dating generally reliable?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2832

Describe how you could determine the percentage of oxygen in air using heated copper.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2833

Explain the principle behind the fractional distillation of air.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2834

What are the two essential conditions for rusting to occur? Describe an experiment to prove both are necessary.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2843

Why is it important to remove water vapour and carbon dioxide from air before it is liquefied for fractional distillation?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2846

Why are cars fitted with catalytic converters? Briefly explain how they reduce pollution.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2847

Why does burning magnesium produce a white powder, while burning sulfur produces a pungent gas? Classify the oxides formed.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2849

If a lake becomes acidic due to acid rain, what substance could be added to neutralize it? What is the chemical process involved?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2850

Why is argon gas often used in light bulbs instead of air?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2852

Why is carbon monoxide dangerous even in small concentrations, and why is it hard to detect?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2853

A student collects oxygen by downward displacement of water. Why is this method preferred over collecting it by upward delivery (air displacement)?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2866

A student set up rusting experiments. Rust only in tube with nail in water exposed to air. Tube with boiled water and oil had no rust. What does this prove?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2868

Write balanced equations for: a) CH₄ + O₂ → b) Fe + O₂ → Fe₃O₄ c) KClO₃ → KCl + O₂ d) SO₂ + O₂ →

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2870

A sample of air contains 0.04% carbon dioxide. What volume of CO₂ is present in 5.0 m³ of air? Express in litres.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2877

How does burning a candle involve both physical and chemical changes?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2880

What is photochemical smog?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2893

Catalytic converters contain precious metals such as and .

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2900

What are the products of incomplete combustion of a hydrocarbon?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2902

What is carbon sequestration?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2903

What is the product of a hydrogen fuel cell?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2905

What device captures soot particles from diesel engine exhaust?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2907

How does acid rain damage forests?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2909

Adding calcium carbonate or calcium hydroxide to acid lakes is called __________.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2910

The fine particles from coal combustion captured by electrostatic precipitators is called .

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2914

Suspended particles in the atmosphere are called __________.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2917

Cylinders of ice drilled from glaciers that contain trapped ancient air bubbles are called .

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2744

What is the principle behind fractional distillation?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2753

A student has a mixture of iodine and sand. Describe how to separate them, explaining why the method works.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2754

You are given a mixture of ethanol (boiling point 78°C) and water. Describe the apparatus and steps you would use to separate them.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2755

Explain why salt spread on icy roads causes the ice to melt, even when the temperature is below 0°C.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2759

Why is the boiling point of a coolant mixture (water and antifreeze) higher than that of pure water? Why is this useful in a car radiator?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2760

How would you obtain pure water from a sample of muddy water? List the steps and name each technique.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2761

Explain the difference between a compound and a mixture, using iron sulfide (FeS) and a mixture of iron and sulfur as examples.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2774

A student runs a chromatogram of a mixture containing two amino acids. A travels 2.8 cm, B travels 5.2 cm, solvent front 8.0 cm. Calculate Rf values. Which is more soluble?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2775

If a pure substance gives an Rf value of 0.65 under specific conditions, and your unknown sample gives the same Rf value under identical conditions, what can you conclude?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2781

What is centrifugation used for?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2785

What is Brownian motion?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2786

The random movement of smoke particles in air is evidence of __________.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2787

The process by which particles clump together in a suspension is called __________.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2792

What is the difference between gravity filtration and vacuum filtration?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2795

How can chromatography be used to identify an unknown substance?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2808

What is recrystallization used for?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2809

Why do different grades of filter paper exist?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2812

Is melting the same as dissolving? Explain.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2813

What is a hydrated salt?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2822

What does a phase diagram show?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2826

Why does evaporation cause cooling?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2827

How does atmospheric pressure affect boiling point?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2828

What is vapor pressure?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2616

Define a drug. What is the difference between medicinal use and drug abuse?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2617

State two social impacts of drug abuse on a community.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2619

Name the apparatus used for: a) measuring exact volume for titration b) grinding solids c) supporting a burette d) holding a hot crucible

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2623

A student mixes sand and salt. Describe a step-by-step procedure to obtain pure dry salt from this mixture.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2624

Explain why copper is used for electrical wiring while plastic is used as an insulating cover.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2625

Why is it dangerous to take antibiotics for a viral infection like the common cold?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2626

How does storing heavy luggage in the lower deck of a bus rather than on the roof relate to stability (centre of gravity)?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2631

Explain how a separating funnel can be used to separate a mixture of oil and water. Why does this work?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2632

Why do athletes sometimes abuse drugs? What are the dangers of performance-enhancing drugs?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2649

A liquid in the lab is suspected to be either pure water or a salt solution. Describe two simple chemical or physical tests (without tasting) to determine which it is.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2653

How is the periodic table organized? What is a group and a period?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2664

What is the maximum number of electrons that can occupy the first three electron shells (n=1,2,3)?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2671

What is metallic bonding?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2682

What is one mole of a substance?

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2693

A substance used in a chemical reaction to detect, measure, or produce other substances is called a __________.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2694

A substance that speeds up a chemical reaction without being consumed is a __________.

MEDIUM +30 XP 5 min

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Completed

CHEMISTRY #2696

The concentration of a solution expressed as moles of solute per liter of solution is called __________.

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CHEMISTRY #2697

How many grams of CO₂ are produced when 1 mole of CH₄ is burned completely? (C=12, O=16)

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CHEMISTRY #2698

Calculate the percentage of oxygen in water (H₂O). (H=1, O=16)

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CHEMISTRY #2703

What is electrolysis?

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CHEMISTRY #2704

In electrolysis, what are the names of the positive and negative electrodes?

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CHEMISTRY #2705

What is a galvanic (voltaic) cell?

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CHEMISTRY #2708

A solution with pH = 3 is __________ times more acidic than pH = 5.

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CHEMISTRY #2709

What is the difference between a strong acid and a weak acid?

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CHEMISTRY #2711

What is the purpose of titration in analytical chemistry?

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CHEMISTRY #2712

List the main equipment needed for an acid-base titration.

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CHEMISTRY #2716

What is an MSDS (Material Safety Data Sheet) and why is it important?

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CHEMISTRY #2721

Why are biodegradable plastics important for the environment?

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CHEMISTRY #2725

What reaction produces an ester?

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CHEMISTRY #2731

What chemical test distinguishes alkenes from alkanes?

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Completed

CHEMISTRY #2732

What is cracking in the petroleum industry?

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CHEMISTRY #2735

What chemicals are primarily responsible for ozone layer depletion?

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Completed

CHEMISTRY #2737

Name two methods to soften hard water.

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Completed

CHEMISTRY #2739

Different structural forms of the same element are called __________.

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PHYSICS #2527

Distinguish between conductors, insulators, and semiconductors in terms of band theory.

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PHYSICS #2529

What are electron-hole pairs? How are they produced?

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Completed

PHYSICS #2531

Define n-type semiconductor. What are majority and minority carriers in n-type?

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Completed

PHYSICS #2532

Define p-type semiconductor. What are majority and minority carriers in p-type?

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Completed

PHYSICS #2535

What is forward bias? Sketch the circuit and describe what happens.

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Completed

PHYSICS #2536

What is reverse bias? Sketch the circuit and describe what happens.

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Completed

PHYSICS #2540

What is the function of a smoothing capacitor in a rectifier circuit?

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Completed

PHYSICS #2542

Silicon has 4 valence electrons. What happens when it is doped with phosphorus (5 valence electrons)?

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Completed

PHYSICS #2543

Silicon has 4 valence electrons. What happens when it is doped with boron (3 valence electrons)?

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Completed

PHYSICS #2548

What is the potential barrier? What is its typical value for silicon?

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Completed

PHYSICS #2550

A silicon diode is forward-biased with 0.5 V. Will it conduct significantly? Why?

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Completed

PHYSICS #2554

Draw a half-wave rectifier circuit with a resistive load.

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Completed

PHYSICS #2555

Sketch the input and output waveforms for a half-wave rectifier.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2556

A half-wave rectifier has an input of 12 V RMS. Calculate: a) Peak input voltage b) Average DC output voltage (without capacitor) c) Peak inverse voltage across diode

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Completed

PHYSICS #2558

Explain why half-wave rectification is inefficient compared to full-wave.

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Completed

PHYSICS #2559

Draw a full-wave rectifier circuit using a center-tapped transformer and two diodes.

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Completed

PHYSICS #2560

Draw a full-wave bridge rectifier circuit using four diodes.

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Completed

PHYSICS #2561

Sketch the input and output waveforms for a full-wave rectifier.

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Completed

PHYSICS #2566

What is the purpose of a smoothing capacitor in a rectifier circuit?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2568

How does increasing the capacitance affect the ripple voltage? What is the trade-off?

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Completed

PHYSICS #2591

The average DC voltage of a full-wave rectifier is __________ times the peak voltage.

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Completed

PHYSICS #2592

A Zener diode operates in the __________ breakdown region to provide voltage regulation.

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Completed

PHYSICS #2599

What is ripple factor?

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Completed

PHYSICS #2602

For a bridge rectifier with secondary RMS voltage Vrms, the PIV rating required for each diode is:

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Completed

PHYSICS #2603

For a center-tapped full-wave rectifier with secondary RMS voltage Vrms (each half), the PIV rating required is:

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Completed

PHYSICS #2604

The band gap energy of silicon at room temperature is approximately __________ eV.

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Completed

PHYSICS #2606

The thermal voltage V_T at temperature T is given by V_T = __________.

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Completed

PHYSICS #2608

Reverse saturation current Iₛ in a diode is highly __________ dependent.

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Completed

PHYSICS #2610

Why is a series resistor required when connecting an LED to a voltage source?

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Completed

PHYSICS #2439

What is a beta-minus particle? What is its origin in the nucleus?

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Completed

PHYSICS #2444

State the two conservation laws that must be satisfied in nuclear equations.

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Completed

PHYSICS #2445

What is carbon dating? What isotope is used?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2449

Explain why alpha particles have high ionizing ability but low penetrating power.

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Completed

PHYSICS #2451

A radioactive source emits radiation that is deflected toward the negative plate in an electric field. What type of radiation is it?

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Completed

PHYSICS #2456

Write the nuclear equation for the alpha decay of Uranium-238.

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Completed

PHYSICS #2457

Write the nuclear equation for the alpha decay of Radium-226.

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Completed

PHYSICS #2458

Write the nuclear equation for the alpha decay of Polonium-210.

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Completed

PHYSICS #2459

Write the nuclear equation for the beta-minus decay of Carbon-14.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2460

Write the nuclear equation for the beta-minus decay of Cobalt-60.

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Completed

PHYSICS #2462

Complete the equation: ²³⁵₉₂U → ? + ⁴₂α

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Completed

PHYSICS #2463

Complete the equation: ⁴⁰₁₉K → ⁴⁰₂₀Ca + ?

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Completed

PHYSICS #2464

Complete the equation: ²³¹₉₀Th → ²³¹₉₁Pa + ?

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Completed

PHYSICS #2465

Complete the equation: ²²²₈₆Rn → ²¹⁸₈₄Po + ?

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Completed

PHYSICS #2469

A radioactive sample has an initial activity of 1200 Bq. After 10 hours, the activity is 300 Bq. Calculate the half-life.

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Completed

PHYSICS #2470

The half-life of strontium-90 is 29 years. How long will it take for a sample to decay to 1/16 of its original mass?

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Completed

PHYSICS #2473

Carbon-14 has a half-life of 5730 years. A bone has 25% of the ¹⁴C found in living bone. How old is it?

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Completed

PHYSICS #2476

Technetium-99m has a half-life of 6 hours. A sample is prepared at 8:00 am with activity 400 MBq. What activity remains at 2:00 pm? At 2:00 am next day?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2478

A wooden tool has activity 4 decays/min/g. Living wood has 16 decays/min/g. Half-life of ¹⁴C is 5730 years. How old is the tool?

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Completed

PHYSICS #2482

Explain how gamma rays are used to sterilize medical equipment.

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Completed

PHYSICS #2485

Explain why alpha emitters are particularly dangerous if ingested or inhaled.

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Completed

PHYSICS #2490

Why is radioactive waste a long-term problem? Give an example of an isotope with a very long half-life.

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Completed

PHYSICS #2497

A Geiger counter records 400 counts per minute from a source. Background is 40 counts/min. What is corrected count rate? After 20 minutes (half-life 10 min), what is corrected rate?

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Completed

PHYSICS #2510

Radioactive waste with very long half-life requires __________ disposal.

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Completed

PHYSICS #2511

Beta-plus decay emits a __________, which is the antiparticle of the electron.

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PHYSICS #2512

Gamma rays are emitted when a nucleus transitions from a __________ state to a lower energy state.

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PHYSICS #2513

__________ is a radioactive gas that can accumulate in basements and is the second leading cause of lung cancer.

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PHYSICS #2515

The unit of activity is the __________ (Bq), equal to one decay per second.

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Completed

PHYSICS #2518

What is the primary source of background radiation exposure for most people?

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Completed

PHYSICS #2521

Calculate the decay constant for carbon-14 (half-life 5730 years) in years⁻¹.

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Completed

PHYSICS #2523

What is the mean life (average lifetime) of a radioactive atom with half-life 8 days?

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Completed

PHYSICS #2525

Specific activity is measured in __________ per kilogram.

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Completed

PHYSICS #2354

State Einstein's photoelectric equation.

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Completed

PHYSICS #2356

What is stopping potential?

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Completed

PHYSICS #2357

How does the maximum kinetic energy of photoelectrons vary with the frequency of incident light?

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Completed

PHYSICS #2361

What is a solar cell? How does it differ from a photocell?

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Completed

PHYSICS #2362

State de Broglie's hypothesis.

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PHYSICS #2365

What is the frequency of a photon with energy 5 eV?

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Completed

PHYSICS #2366

A photon has energy 3.2 × 10⁻¹⁹ J. Calculate its wavelength in nm.

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Completed

PHYSICS #2368

Compare the energy of a photon of radio waves (f = 100 MHz) with that of an X-ray photon (f = 3 × 10¹⁸ Hz).

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Completed

PHYSICS #2369

The work function of potassium is 2.0 eV. Calculate: a) The threshold frequency b) The threshold wavelength

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PHYSICS #2370

Light of wavelength 500 nm shines on a sodium surface (work function = 2.28 eV). Will photoelectrons be emitted? If so, find their maximum kinetic energy.

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Completed

PHYSICS #2372

The stopping potential for photoelectrons from a metal surface is 0.8 V when illuminated by light of wavelength 450 nm. Calculate: a) The maximum kinetic energy of electrons b) The work function of the metal

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Completed

PHYSICS #2373

When light of wavelength 400 nm falls on a metal, the stopping potential is 1.2 V. Find the work function and the threshold wavelength.

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Completed

PHYSICS #2374

A metal has a threshold wavelength of 600 nm. Calculate the work function in eV. What is the maximum kinetic energy of electrons if light of wavelength 400 nm is used?

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Completed

PHYSICS #2377

The slope of a Vₛ vs f graph is 4.1 × 10⁻¹⁵ V/Hz. Calculate Planck's constant.

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PHYSICS #2380

A photocell has a sensitivity of 0.05 A/W. What current is produced when illuminated by light of power 2 mW?

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PHYSICS #2381

A solar panel of area 2 m² receives solar radiation of 800 W/m². If its efficiency is 15%, calculate the electrical power output.

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PHYSICS #2383

A photocell is used in an automatic door system. Explain how it works.

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Completed

PHYSICS #2385

A solar cell has an open-circuit voltage of 0.6 V and a short-circuit current of 2 A under full illumination. What is the maximum power output? (Assume fill factor = 0.75)

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2393

A solar panel in space receives 1400 W/m² of solar radiation. Its area is 10 m² and efficiency is 20%. Calculate the power output. If the panel's voltage is 50 V, what current does it deliver?

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Completed

PHYSICS #2399

The threshold frequency is given by f₀ = __________.

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Completed

PHYSICS #2400

The stopping potential is related to maximum kinetic energy by __________.

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Completed

PHYSICS #2405

The product hc is approximately __________ eV·nm.

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PHYSICS #2407

What is the energy of a 10 MHz radio photon in eV?

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PHYSICS #2409

Cesium has work function 2.1 eV. What is the threshold wavelength? Will blue light (450 nm) eject electrons?

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PHYSICS #2410

Copper has work function 4.7 eV. What is the threshold wavelength? Will visible light (400-700 nm) eject electrons?

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Completed

PHYSICS #2411

In an experiment, stopping potential vs frequency gives slope 4.2×10⁻¹⁵ V/Hz. Calculate h.

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PHYSICS #2413

Light of 200 nm hits metal with work function 4.0 eV. Find KE_max in eV and J.

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PHYSICS #2414

Metal Φ=3.0 eV, light λ=300 nm. Find stopping potential.

MEDIUM +30 XP 5 min

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PHYSICS #2415

A spacecraft has solar panels of area 50 m² with efficiency 30% at Earth orbit (1400 W/m²). What power is generated? At Mars (590 W/m²), what power?

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Completed

PHYSICS #2417

Mercury has work function 4.5 eV. What is the threshold frequency? What wavelength of UV is needed?

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PHYSICS #2419

Name three devices that utilize the photoelectric effect.

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PHYSICS #2420

What evidence supports wave-particle duality for light?

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PHYSICS #2421

Calculate the de Broglie wavelength of an electron moving at 1×10⁶ m/s. (m=9.1×10⁻³¹ kg, h=6.63×10⁻³⁴ J s)

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PHYSICS #2425

The cathode in a visible-light photocell is often coated with __________, which has a low work function.

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PHYSICS #2427

What is "dark current" in a photocell?

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PHYSICS #2432

What is the significance of Planck's constant h in quantum mechanics?

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PHYSICS #2262

What is the principle of an X-ray tube?

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PHYSICS #2265

Why is tungsten used as the target material in an X-ray tube?

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PHYSICS #2267

Why is a high vacuum necessary in an X-ray tube?

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PHYSICS #2272

List four properties of X-rays.

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PHYSICS #2274

What are the biological hazards of X-ray exposure?

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PHYSICS #2276

What is the ALARA principle?

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PHYSICS #2278

What is a half-value layer (HVL)?

MEDIUM +30 XP 5 min

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PHYSICS #2280

Calculate the minimum wavelength produced by an X-ray tube operating at 100 kV. (h = 6.63 × 10⁻³⁴ J s, c = 3 × 10⁸ m/s, e = 1.6 × 10⁻¹⁹ C)

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PHYSICS #2281

An X-ray tube has a tube current of 20 mA and operates at 80 kV. Calculate: a) The power input to the tube b) The number of electrons striking the target per second

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Completed

PHYSICS #2282

If only 1% of the electron energy is converted to X-rays in the tube of question 2281, what is the X-ray power output?

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Completed

PHYSICS #2283

Explain how increasing the filament current affects the X-ray beam.

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Completed

PHYSICS #2287

Calculate the frequency of an X-ray photon with energy 50 keV.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2292

Calculate the energy in keV of X-rays with wavelength 0.15 nm. Are these hard or soft?

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Completed

PHYSICS #2296

Describe an experiment to demonstrate that X-rays travel in straight lines.

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Completed

PHYSICS #2298

Explain why X-rays are not deflected by electric or magnetic fields.

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PHYSICS #2301

If the half-value layer for a material is 5 mm, what thickness is needed to reduce the intensity to 12.5% of its original value?

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PHYSICS #2302

Compare the penetrating power of X-rays through lead, bone, and soft tissue. Explain why X-ray images show contrast.

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PHYSICS #2305

A radiographer stands 2 m from an X-ray source and receives a dose rate of 50 μSv/h. What would be the dose rate at 4 m?

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Completed

PHYSICS #2308

What is the purpose of a film badge or TLD worn by radiation workers?

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PHYSICS #2309

Explain why X-ray rooms have lead-lined walls and warning lights.

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PHYSICS #2314

A patient receives a dose of 0.1 Sv during a CT scan. If the risk of fatal cancer is approximately 5% per sievert, what is the estimated increase in risk for this patient?

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PHYSICS #2323

About __________% of electron energy converts to heat in the anode.

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PHYSICS #2324

X-rays produced by deceleration of electrons are called __________ radiation.

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PHYSICS #2327

The minimum wavelength of X-rays is inversely proportional to the __________ voltage.

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PHYSICS #2330

X-rays cause certain materials to __________, emitting visible light.

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PHYSICS #2334

Calculate the energy in joules of an X-ray photon with wavelength 0.01 nm.

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Completed

PHYSICS #2335

An X-ray tube operates at 15 mA. How many electrons strike the target per second?

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Completed

PHYSICS #2339

A material transmits 25% of incident X-rays through 2 cm. Calculate the HVL.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2342

How does a Geiger-Müller tube detect X-rays?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2345

Why are contrast agents like barium or iodine used in X-ray imaging?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2346

What does "lead equivalence" mean for an X-ray protective material?

MEDIUM +30 XP 5 min

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PHYSICS #2107

What is a ring main circuit?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2110

How do you choose the correct fuse rating for an appliance?

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Completed

PHYSICS #2111

What is a consumer unit (fuse box)?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2113

What is double insulation?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2117

Power station generates 100 MW at 25 kV. Calculate current.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2119

Same 100 MW stepped up to 400 kV. Calculate new current.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2123

Explain why power loss is proportional to I² rather than I.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2125

3 kW heater at 230 V. Calculate current and suggest fuse rating.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2127

Kettle 2.2 kW, 230 V. Calculate current and recommended fuse rating.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2128

Hair dryer draws 4 A at 230 V. Find power and suitable fuse.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2129

Explain why the earth wire is connected to the metal case of a washing machine.

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PHYSICS #2130

What happens if a fault causes the live wire to touch the metal case of an earthed appliance?

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PHYSICS #2132

What is the purpose of the cable grip in a plug?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2138

Meter: 6543 kWh on 1st March, 6721 kWh on 1st April. Tariff 32p/kWh. Find cost for March.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2139

60 W fan runs 8 h/day for 30 days. Tariff 25p/kWh. Find cost.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2151

Household uses 800 kWh in a quarter. Standing charge £15, unit rate 30p/kWh. Find total bill.

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Completed

PHYSICS #2162

The correct fuse rating should be slightly __________ than the normal current.

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PHYSICS #2164

An RCD protects against __________.

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PHYSICS #2171

Power stations typically generate electricity at around __________ kV.

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PHYSICS #2175

The heating element in a kettle is made of __________ because it has high resistance and doesn't oxidise easily.

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PHYSICS #2176

The highest voltage transmission lines in the UK are typically __________ kV.

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PHYSICS #2179

A __________ meter sends real-time electricity usage data to the supplier.

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PHYSICS #2182

Explain the process of thermionic emission.

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PHYSICS #2185

What is the function of the control grid in a CRO?

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Completed

PHYSICS #2186

How is the brightness of the trace controlled in a CRO?

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PHYSICS #2191

What is fluorescence? Why is it important in a CRO?

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PHYSICS #2195

What is the time base in a CRO? What waveform does it produce?

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PHYSICS #2196

Explain how a CRO can be used to measure a DC voltage.

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PHYSICS #2197

Explain how a CRO can be used to measure the frequency of an AC signal.

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PHYSICS #2200

Explain why a high vacuum is necessary in a cathode ray tube.

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PHYSICS #2201

An electron accelerated through 2500 V. Calculate its kinetic energy in joules. (e = 1.6 × 10⁻¹⁹ C)

MEDIUM +30 XP 5 min

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Completed

PHYSICS #2204

CRO: accelerating voltage 1500 V, beam current 0.2 mA. Calculate beam power.

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PHYSICS #2207

If accelerating voltage is doubled, what happens to kinetic energy?

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PHYSICS #2209

The control grid is made more negative. What effect does this have on the trace?

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PHYSICS #2217

Sine wave peak-to-peak height 6.2 divisions, Y-gain = 5 V/div. Find V_pp.

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PHYSICS #2218

Same waveform, find peak voltage.

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PHYSICS #2220

Y-gain = 2 V/div, waveform occupies 4.5 divisions top to bottom. Find peak voltage.

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Completed

PHYSICS #2221

Square wave amplitude 3 divisions above and below centre. Y-gain = 0.5 V/div. Find V_pp and V_peak.

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Completed

PHYSICS #2222

Unknown DC voltage: Y-gain 0.2 V/div, deflection 5.5 divisions. Find voltage. If Y-gain changed to 0.5 V/div, new deflection?

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Completed

PHYSICS #2223

Time base = 2 ms/div, one cycle occupies 4 divisions. Find period and frequency.

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Completed

PHYSICS #2224

100 Hz signal, time base = 5 ms/div. How many divisions per cycle?

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PHYSICS #2225

2 kHz signal, time base = 0.1 ms/div. How many divisions per cycle?

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Completed

PHYSICS #2251

The __________ generates a sawtooth voltage for horizontal sweeping.

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PHYSICS #2255

The peak voltage of a sine wave is __________ times the RMS voltage.

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PHYSICS #2258

The time base generates a __________ wave.

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PHYSICS #2001

What is magnetic flux?

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PHYSICS #2003

What is magnetic flux linkage?

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Completed

PHYSICS #2004

What does Faraday's Law of electromagnetic induction state?

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PHYSICS #2005

What does Lenz's Law state?

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PHYSICS #2008

What is mutual induction?

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PHYSICS #2009

Coil area 0.02 m², 50 turns, perpendicular to B=0.4 T. Calculate flux linkage.

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PHYSICS #2010

100 turns, flux changes 0.01 Wb to 0.05 Wb in 0.2 s. Find average e.m.f.

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Completed

PHYSICS #2011

200 turns, flux 0.03 Wb reduced to zero in 0.1 s. Find induced e.m.f.

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PHYSICS #2018

A coil is placed in a magnetic field that is increasing. What is the direction of induced current?

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PHYSICS #2019

A coil is placed in a magnetic field that is decreasing. What is the direction of induced current?

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PHYSICS #2022

Describe the construction of an AC generator.

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PHYSICS #2029

What is the purpose of the iron core in the coil of a generator?

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PHYSICS #2030

How does the frequency of the output from an AC generator depend on the speed of rotation?

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PHYSICS #2034

Why are transformers used in power transmission?

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PHYSICS #2040

Ideal transformer: primary 240 V, 2 A; secondary 12 V. Find secondary current.

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PHYSICS #2049

Why is high voltage used for long-distance power transmission?

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PHYSICS #2053

Faraday's Law states that induced e.m.f. is proportional to the rate of change of __________.

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PHYSICS #2065

Transformer cores are laminated to reduce __________ currents.

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PHYSICS #2067

Eddy currents are __________ currents induced in the core that cause heating.

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PHYSICS #2070

The motional e.m.f. induced in a conductor moving perpendicular to a magnetic field is E = __________.

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PHYSICS #2075

Large transformers are often cooled using __________ to dissipate heat.

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PHYSICS #2079

Faraday's original experiment showed that moving a magnet into a coil produces a temporary __________.

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PHYSICS #2080

The SI unit of inductance is the __________.

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PHYSICS #2082

The efficiency of a generator is the ratio of electrical power output to __________ power input.

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Completed

PHYSICS #2089

Copper losses in a transformer are also called __________ losses.

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PHYSICS #2091

Grid transformers that step down voltage for distribution to homes are often mounted on __________.

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PHYSICS #2094

Transformer oil acts as both an __________ and a coolant.

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PHYSICS #1904

Why can electromagnetic waves travel through a vacuum while sound waves cannot?

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Completed

PHYSICS #1913

What is meant by "ionizing radiation"?

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PHYSICS #1914

Which parts of the EM spectrum are ionizing?

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PHYSICS #1915

What is the relationship between frequency and energy of EM waves?

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PHYSICS #1916

What is the formula for the energy of a photon?

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PHYSICS #1918

X-ray wavelength 0.1 nm. Calculate frequency.

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Completed

PHYSICS #1920

Visible light frequency 5 × 10¹⁴ Hz. Find wavelength.

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Completed

PHYSICS #1921

Gamma rays frequency 3 × 10²⁰ Hz. Find wavelength.

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Completed

PHYSICS #1923

Radar signal returns after 4 × 10⁻⁴ s. How far is the aircraft?

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PHYSICS #1924

FM station broadcasts at 98.5 MHz. Find wavelength.

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PHYSICS #1925

How are radio waves produced artificially?

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Completed

PHYSICS #1926

What is the function of an aerial in a radio transmitter and receiver?

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Completed

PHYSICS #1928

What is the source of microwaves in a microwave oven?

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PHYSICS #1930

How does radar work?

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Completed

PHYSICS #1933

Why are microwaves used in mobile phone communication?

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Completed

PHYSICS #1934

What safety precautions are necessary when using microwave ovens?

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Completed

PHYSICS #1936

How is infrared detected?

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PHYSICS #1939

Why is infrared used in TV remote controls?

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PHYSICS #1944

What are the three types of UV radiation?

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PHYSICS #1947

List three beneficial uses of ultraviolet radiation.

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PHYSICS #1950

Why do some banknotes fluoresce under UV light?

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PHYSICS #1952

How does sunscreen protect the skin from UV?

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PHYSICS #1953

Why do welders wear special goggles?

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PHYSICS #1955

Why are X-rays used in medical imaging?

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PHYSICS #1959

What are the dangers of X-ray exposure?

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PHYSICS #1965

How are gamma rays used to sterilize medical equipment?

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Completed

PHYSICS #1966

Arrange the following in order of increasing wavelength: UV, radio, gamma, infrared, visible, X-ray, microwave.

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Completed

PHYSICS #1967

Arrange in increasing frequency: microwave, visible, gamma, radio, X-ray, infrared, UV.

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PHYSICS #1989

X-rays are produced when high-speed __________ strike a metal target.

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PHYSICS #1990

Gamma rays originate from the __________ of atoms.

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PHYSICS #1991

and are ionizing radiations.

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PHYSICS #1994

__________ are used to sterilize medical equipment.

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Completed

PHYSICS #1996

The energy of a photon is given by E = __________.

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Completed

PHYSICS #1721

What is the lens formula?

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Completed

PHYSICS #1722

What is the magnification formula for lenses?

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Completed

PHYSICS #1723

What is accommodation of the eye?

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Completed

PHYSICS #1730

What is presbyopia?

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Completed

PHYSICS #1732

What is the principle of a simple microscope (magnifying glass)?

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Completed

PHYSICS #1733

What is the function of the objective lens in a compound microscope?

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Completed

PHYSICS #1734

What is the function of the eyepiece in a compound microscope?

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Completed

PHYSICS #1735

What is the magnifying power of a telescope in normal adjustment?

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Completed

PHYSICS #1736

What is the length of an astronomical telescope in normal adjustment?

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Completed

PHYSICS #1740

Real image at 40 cm, object at 20 cm. Find focal length.

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Completed

PHYSICS #1751

Two lenses +2 D and -3 D in contact. Find power and focal length.

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Completed

PHYSICS #1758

Magnifying glass f=4 cm. Find M (image at infinity) and M (image at near point D=25 cm).

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Completed

PHYSICS #1759

Magnifying glass f=5 cm. Find M when image at near point (D=25 cm).

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Completed

PHYSICS #1760

Astronomical telescope f₀=100 cm, fₑ=5 cm. Find magnifying power and tube length.

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Completed

PHYSICS #1761

Telescope f₀=150 cm, fₑ=2.5 cm. Find M and L.

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Completed

PHYSICS #1762

Telescope M=20 (magnitude), fₑ=5 cm. Find f₀ and L.

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Completed

PHYSICS #1774

The lens formula is __________.

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Completed

PHYSICS #1775

Magnification m = / = / .

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Completed

PHYSICS #1776

For a real image, v is __________.

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Completed

PHYSICS #1777

For a virtual image, v is __________.

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Completed

PHYSICS #1781

The ability of the eye to focus on objects at different distances is called __________.

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Completed

PHYSICS #1782

In a simple microscope, the object is placed between and .

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Completed

PHYSICS #1783

In a compound microscope, the objective forms a , , __ image.

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Completed

PHYSICS #1793

When an object is placed at 2F of a convex lens, the image is at , , and __ size.

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Completed

PHYSICS #1794

When an object is placed at the focus of a convex lens, the image is at __________.

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PHYSICS #1795

When an object is placed between F and O of a convex lens, the image is , , and __.

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Completed

PHYSICS #1797

The magnifying power of an astronomical telescope in normal adjustment is M = __________.

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Completed

PHYSICS #1635

What is the main difference between streamline and turbulent flow in terms of energy loss?

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Completed

PHYSICS #1636

What does the equation of continuity state?

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PHYSICS #1637

What physical law does the equation of continuity represent?

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Completed

PHYSICS #1640

What does Bernoulli's Principle state?

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PHYSICS #1642

What is the simplified Bernoulli's equation for horizontal flow?

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Completed

PHYSICS #1643

How does an airplane wing generate lift?

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Completed

PHYSICS #1644

How does a Bunsen burner draw in air when the gas is turned on?

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Completed

PHYSICS #1645

Why is it dangerous to stand too close to the edge of a platform when a high-speed train passes?

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Completed

PHYSICS #1647

A curtain is sometimes pulled out of an open window. How does this happen?

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Completed

PHYSICS #1652

Where is turbulent flow undesirable?

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Completed

PHYSICS #1657

River: section1 width 10 m, depth 2 m, v₁=0.5 m/s. Section2 width 8 m, depth 2.5 m. Find v₂.

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Completed

PHYSICS #1659

Pipe diameter 0.1 m (r=0.05 m, A=0.00785 m²), v=3 m/s. Find flow rate in m³/s and L/s.

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Completed

PHYSICS #1665

Water tank height 5 m, hole at depth 2 m below surface. Find exit velocity.

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Completed

PHYSICS #1668

Water tank height 10 m, hole at base. Find exit velocity.

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Completed

PHYSICS #1679

A Bunsen burner works by creating a region of __________ pressure at the base, which draws in air.

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Completed

PHYSICS #1680

The simplified Bernoulli's equation for horizontal flow is __________.

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Completed

PHYSICS #1682

In a Venturi meter, the pressure is __________ at the constriction.

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Completed

PHYSICS #1683

The curving of a spinning ball in flight is called the __________ Effect.

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Completed

PHYSICS #1684

The speed of efflux from a hole in a tank is v = __________.

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Completed

PHYSICS #1688

The term ½ρv² in Bernoulli's equation is called __________ pressure.

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Completed

PHYSICS #1689

The term P in Bernoulli's equation is called __________ pressure.

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Completed

PHYSICS #1692

How does a chimney create draught (air flow)?

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Completed

PHYSICS #1693

Why are water towers built on high ground?

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Completed

PHYSICS #1697

Why do some sports cars have rear spoilers?

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PHYSICS #1700

What type of flow occurs at very low Reynolds numbers?

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PHYSICS #1703

Bernoulli's principle assumes the fluid is __________ (no viscosity).

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PHYSICS #1704

Bernoulli's principle assumes the fluid is __________ (density constant).

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PHYSICS #1705

Bernoulli's principle assumes __________ flow (not changing with time).

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PHYSICS #1707

The reduction in pressure at a constriction in a pipe is called the __________ effect.

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PHYSICS #1708

The formula v = √(2gh) for efflux speed is known as __________'s theorem.

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PHYSICS #1709

The lift generated by a moving object in a fluid is called __________ lift.

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Completed

PHYSICS #1562

What does Snell's Law state?

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Completed

PHYSICS #1569

What is the critical angle?

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Completed

PHYSICS #1571

What is the mathematical relationship between refractive index (n) and critical angle (c)?

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Completed

PHYSICS #1574

Why does a swimming pool appear shallower than its actual depth?

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PHYSICS #1576

How does an optical fibre work?

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Completed

PHYSICS #1582

A coin at the bottom of an empty cup disappears when you move back, then reappears when water is added. Why?

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PHYSICS #1583

What is the advantage of using TIR in optical fibres over using mirrors?

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Completed

PHYSICS #1584

Light strikes glass at i=40°, r=25°. Calculate refractive index of glass.

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Completed

PHYSICS #1586

Speed of light in diamond is 1.24×10⁸ m/s. Find refractive index. (c=3.0×10⁸ m/s)

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Completed

PHYSICS #1587

Water appears 1.2 m deep. n=4/3. Find real depth.

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Completed

PHYSICS #1588

Coin in liquid n=1.6, depth 24 cm. Find apparent depth.

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Completed

PHYSICS #1589

Light from air into glass (n=1.5) at i=50°. Find r.

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Completed

PHYSICS #1591

Glass n=1.6. Find speed of light in glass. (c=3×10⁸ m/s)

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Completed

PHYSICS #1594

Critical angle for a medium is 42°. Calculate n.

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Completed

PHYSICS #1595

Calculate critical angle for water (n=4/3).

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Completed

PHYSICS #1596

Calculate critical angle for diamond (n=2.42).

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Completed

PHYSICS #1597

A glass has critical angle 41°. Find n.

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Completed

PHYSICS #1610

Snell's Law is given by the formula __________.

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Completed

PHYSICS #1617

The critical angle for water (n=4/3) is approximately __________.

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Completed

PHYSICS #1618

The critical angle for glass (n=1.5) is approximately __________.

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Completed

PHYSICS #1619

The critical angle for diamond (n=2.42) is approximately __________.

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Completed

PHYSICS #1624

The apparent depth is given by d_app = d_real / n when viewed from __________.

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Completed

PHYSICS #1625

Real depth = n × d_app when viewing from __________.

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Completed

PHYSICS #1626

What principle allows an endoscope to see inside the human body?

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PHYSICS #1628

Why does a prism split white light into colours?

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Completed

PHYSICS #1630

What does a refractive index of 1 mean?

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Completed

PHYSICS #1487

Why does a falling object reach terminal velocity?

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Completed

PHYSICS #1496

Same lift accelerates upwards at 2 m/s². Find spring balance reading.

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Completed

PHYSICS #1497

Same lift accelerates downwards at 3 m/s². Find spring balance reading.

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Completed

PHYSICS #1498

Same lift falls freely (cable breaks). Find spring balance reading.

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Completed

PHYSICS #1503

How does a rocket work in the vacuum of space? What does it push against?

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PHYSICS #1504

Why is it difficult to walk on a frictionless surface?

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PHYSICS #1505

When you jump off a small boat onto a dock, the boat moves backwards. Why?

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PHYSICS #1506

In a collision between a heavy truck and a small car, which experiences the greater force?

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PHYSICS #1507

In the same collision, which experiences the greater acceleration?

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PHYSICS #1514

What is the relationship between impulse and change in momentum?

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PHYSICS #1516

How does an airbag reduce injury during a car crash?

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PHYSICS #1517

Why do cricketers pull their hands backwards when catching a fast ball?

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Completed

PHYSICS #1518

A 0.5 kg ball at 12 m/s is caught in 0.05 s. Find change in momentum.

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PHYSICS #1519

Same ball, find average force exerted by ball on hands.

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PHYSICS #1525

What does the Law of Conservation of Linear Momentum state?

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PHYSICS #1529

2 kg trolley at 3 m/s collides with stationary 1 kg trolley and they stick. Find common velocity.

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Completed

PHYSICS #1530

10 g bullet fired from 2 kg gun at 400 m/s. Find recoil velocity of gun.

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Completed

PHYSICS #1534

50 kg girl jumps from 100 kg boat at 2 m/s. Find boat velocity.

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Completed

PHYSICS #1553

A 2 kg ball is projected upwards at 15 m/s. What is its momentum at the highest point?

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Completed

PHYSICS #1556

At terminal velocity, what is the net force on the falling object?

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Completed

PHYSICS #1558

In a lift, the apparent weight (T) is: T = m(g+a) when accelerating , and T = m(g-a) when accelerating .

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Completed

PHYSICS #1560

Which law explains why a rocket can accelerate in space?

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Completed

PHYSICS #1404

When is no work done by a force?

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Completed

PHYSICS #1414

A ball is thrown upwards. What energy changes occur?

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PHYSICS #1420

Why can a powerful engine accelerate a car faster than a less powerful engine of the same mass?

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PHYSICS #1424

What is the relationship between MA, VR, and efficiency?

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PHYSICS #1426

Why is a long ramp easier to use to lift heavy objects onto a truck than a short, steep ramp?

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PHYSICS #1429

Which is an example of a first-class lever in the human body?

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Completed

PHYSICS #1430

Why is a block and tackle system with many pulleys easier to lift a heavy load? What is the trade-off?

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Completed

PHYSICS #1435

2 kg ball dropped from 20 m. Velocity just before impact? (g=10 m/s², ignore air resistance)

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Completed

PHYSICS #1437

Crane lifts 500 kg to 20 m in 10 s. Find work done. (g=10 m/s²)

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PHYSICS #1438

Same crane, find power developed.

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PHYSICS #1439

Car engine: force 1500 N, constant speed 30 m/s. Find power.

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Completed

PHYSICS #1440

1000 kg car from rest to 20 m/s in 5 s. Find gain in KE.

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Completed

PHYSICS #1441

Same car, find average power developed.

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Completed

PHYSICS #1443

Lever: load 400 N, load distance 0.3 m, effort distance 1.2 m. Find ideal effort.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1445

Same lever, find velocity ratio.

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Completed

PHYSICS #1448

Same system (VR=5, MA=4). Find efficiency.

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Completed

PHYSICS #1451

Same incline (VR=4, MA=3). Find efficiency.

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Completed

PHYSICS #1454

Same incline: work input 1200 J, work output 900 J. Find work against friction.

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Completed

PHYSICS #1456

Same wheel: effort 80 N, 100% efficiency. Find max load.

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Completed

PHYSICS #1460

Same pulley (MA=1.875, VR=2). Find efficiency.

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Completed

PHYSICS #1461

Second-class lever: load 800 N, load distance 0.4 m, effort distance 1.6 m. Find ideal effort.

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Completed

PHYSICS #1463

VR=4, efficiency 80%, load 1200 N. Find MA.

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Completed

PHYSICS #1464

Same system, find effort required.

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Completed

PHYSICS #1470

Same experiment (work output 400 J, work input 480 J). Find efficiency.

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Completed

PHYSICS #1472

Same block, find velocity at bottom using energy.

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Completed

PHYSICS #1474

2 kg ball thrown up at 15 m/s. Max height using energy?

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Completed

PHYSICS #1325

What is the difference between an ohmic and a non-ohmic conductor?

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Completed

PHYSICS #1326

What does the V-I characteristic graph for a filament lamp look like?

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Completed

PHYSICS #1329

What is electromotive force (e.m.f.) of a cell?

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Completed

PHYSICS #1330

What is internal resistance?

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Completed

PHYSICS #1331

What is the equation relating e.m.f. (ε), terminal voltage (V), current (I), and internal resistance (r)?

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Completed

PHYSICS #1333

What is a kilowatt-hour (kWh)?

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Completed

PHYSICS #1334

How many joules are in 1 kilowatt-hour?

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Completed

PHYSICS #1335

Why do birds sitting on a high-voltage power line not get electrocuted?

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Completed

PHYSICS #1336

Why does a filament lamp not obey Ohm's Law?

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Completed

PHYSICS #1340

Why is it more economical to transmit electrical power at high voltages?

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Completed

PHYSICS #1347

8 Ω and 12 Ω in parallel. Find total resistance.

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Completed

PHYSICS #1348

Two 6 Ω in parallel, then in series with 4 Ω. Find total R.

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Completed

PHYSICS #1349

20 Ω and 30 Ω in parallel, then in series with 10 Ω. Find total R.

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Completed

PHYSICS #1352

Cell ε=2.0 V, r=0.1 Ω, external R=3.9 Ω. Find current.

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Completed

PHYSICS #1353

Same cell, find terminal voltage.

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Completed

PHYSICS #1355

Battery ε=12 V, r=0.5 Ω, I=2 A. Find terminal voltage.

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Completed

PHYSICS #1356

Same battery, find external resistance.

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Completed

PHYSICS #1359

Battery ε=6 V, r=2 Ω. What is the maximum current it can deliver?

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Completed

PHYSICS #1360

Same battery, what is terminal voltage when delivering maximum current?

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Completed

PHYSICS #1361

Two cells: each ε=1.5 V, r=0.2 Ω, connected in series to R=2.6 Ω. Find total ε and r.

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Completed

PHYSICS #1362

Same circuit, find current.

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Completed

PHYSICS #1363

Same circuit, find terminal voltage.

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Completed

PHYSICS #1369

Same heater, find energy in joules.

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Completed

PHYSICS #1370

Same heater, find energy in kWh.

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Completed

PHYSICS #1371

2.5 kW kettle used for 30 minutes. Find energy in kWh and cost at $0.12/kWh.

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Completed

PHYSICS #1372

Motor lifts 50 kg, 10 m in 5 s. Input: 240 V, 2.5 A. Find electrical power input.

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Completed

PHYSICS #1373

Same motor, find mechanical power output.

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Completed

PHYSICS #1375

100 W lamp used 5 h/day for 30 days. Cost $0.15/kWh. Find total cost.

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Completed

PHYSICS #1376

500 W heater heats 2 kg water from 20°C to 100°C. c=4200 J/kg°C. Find energy required.

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Completed

PHYSICS #1378

100 W lamp for 250 V. Find resistance.

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Completed

PHYSICS #1379

Same lamp on 200 V. Find power (assuming constant R).

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Completed

PHYSICS #1381

12 V battery, r=1 Ω, parallel combination of 6 Ω and 3 Ω. Find external resistance.

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Completed

PHYSICS #1382

Same circuit, find total current.

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Completed

PHYSICS #1385

Same circuit, find terminal voltage.

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Completed

PHYSICS #1395

The e.m.f. of a cell is the voltage when __________ current is flowing.

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Completed

PHYSICS #1396

The voltage lost inside a cell due to internal resistance is given by __________.

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Completed

PHYSICS #1397

The terminal voltage V = ε - __________.

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Completed

PHYSICS #1398

Electrical power can be calculated using P = VI = = .

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Completed

PHYSICS #1253

What causes a wave to refract?

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Completed

PHYSICS #1255

Under what condition is diffraction most noticeable?

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Completed

PHYSICS #1256

Why can you hear sound around a corner but cannot see light around a corner?

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Completed

PHYSICS #1259

What is the principle of superposition?

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Completed

PHYSICS #1264

In a double-slit experiment, what happens to fringe spacing if wavelength increases?

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Completed

PHYSICS #1265

In a double-slit experiment, what happens to fringe spacing if slits are moved closer together?

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Completed

PHYSICS #1266

In a double-slit experiment, what happens to fringe spacing if the screen is moved further away?

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Completed

PHYSICS #1267

What is a stationary (standing) wave?

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PHYSICS #1268

How is a stationary wave formed on a guitar string?

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Completed

PHYSICS #1274

What is the general equation for a progressive wave travelling in the positive x-direction?

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PHYSICS #1277

What is angular frequency (ω)?

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Completed

PHYSICS #1278

What is wave number (k)?

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Completed

PHYSICS #1279

What is the phase of a wave?

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Completed

PHYSICS #1282

What happens when a wave pulse reaches a fixed end?

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Completed

PHYSICS #1283

What happens when a wave pulse reaches a free end?

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Completed

PHYSICS #1292

Distance between first and third node is 0.5 m. Find wavelength.

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Completed

PHYSICS #1293

Closed pipe length 0.34 m, fundamental frequency 250 Hz. Find wavelength.

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Completed

PHYSICS #1294

Same pipe (λ = 1.36 m, f = 250 Hz). Find speed of sound.

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Completed

PHYSICS #1295

Open pipe length 0.5 m, v = 340 m/s. Find fundamental frequency.

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Completed

PHYSICS #1296

Same pipe, find first overtone (second harmonic) frequency.

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Completed

PHYSICS #1302

Same equation, find frequency.

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Completed

PHYSICS #1303

Same equation, find wavelength.

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Completed

PHYSICS #1304

Same equation, find wave speed.

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Completed

PHYSICS #1306

ω = 314 rad/s. Find frequency.

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Completed

PHYSICS #1307

k = 2 rad/m. Find wavelength.

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Completed

PHYSICS #1310

Two points 0.5 m apart, λ = 2 m. Find phase difference.

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Completed

PHYSICS #1192

What are the rules for drawing electric field lines?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1194

What is the direction of an electric field?

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Completed

PHYSICS #1195

Why is the electric field between parallel plates considered uniform?

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Completed

PHYSICS #1196

What happens at the edges of parallel plates?

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Completed

PHYSICS #1205

What is one farad?

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Completed

PHYSICS #1206

Why are practical capacitors measured in μF, nF, or pF?

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Completed

PHYSICS #1207

What three factors affect the capacitance of a parallel plate capacitor?

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Completed

PHYSICS #1211

How does inserting a dielectric affect capacitance?

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Completed

PHYSICS #1212

What is the dielectric constant (κ)?

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Completed

PHYSICS #1213

Where is energy stored in a capacitor?

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Completed

PHYSICS #1214

What is the formula for energy stored in a capacitor?

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Completed

PHYSICS #1218

How does the total capacitance in series compare to the smallest individual capacitance?

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Completed

PHYSICS #1219

How does the total capacitance in parallel compare to the individual capacitances?

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Completed

PHYSICS #1224

+2 μC charge in uniform E field of 1000 N/C. Calculate force.

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Completed

PHYSICS #1227

10 μF capacitor connected to 12 V. Find charge and energy.

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Completed

PHYSICS #1228

Area 0.1 m², separation 0.001 m, air (ε₀ = 8.85×10⁻¹² F/m). Find C.

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Completed

PHYSICS #1234

4 μF and 12 μF in series. Find total C.

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Completed

PHYSICS #1240

Three equal capacitors C in series. Total C?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1134

Why is the heating effect undesirable in power transmission lines?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1135

Why does doubling the current through a heater quadruple the heat produced?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1136

Why are heating elements made of high-resistance materials like nichrome?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1138

How does a fuse work?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1139

How do you choose the correct fuse rating for an appliance?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1143

Why is earthing important for safety?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1144

What is double insulation?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1145

Which of these appliances typically has double insulation?

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Completed

PHYSICS #1148

What is the purpose of the cable grip in a plug?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1150

What is an RCD (Residual Current Device)?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1152

What is a ring main circuit?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1153

What is an advantage of a ring main circuit over a radial circuit?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1154

Where is a radial circuit typically used?

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Completed

PHYSICS #1155

3 A through 10 Ω resistor for 2 minutes. Calculate heat produced.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1156

240 V kettle with 30 Ω resistance. Heat in 5 minutes.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1157

Heater draws 4 A from 230 V supply. Heat in 1 hour in kJ.

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Completed

PHYSICS #1158

2 A for 10 minutes produces 24,000 J of heat. Find resistance.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1159

500 W heater used for 30 minutes. Heat in Joules and kWh.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1161

12 V battery connected to 6 Ω resistor for 5 minutes. Find current and heat.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1162

Iron draws 5 A from 230 V supply. Find power and heat in 10 minutes.

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Completed

PHYSICS #1163

60 W lamp on 230 V. Calculate current and suggest fuse rating.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1164

1.2 kW kettle on 230 V. Calculate current and suggest fuse rating.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1165

2.5 kW heater on 230 V. Calculate current and suggest fuse rating.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1166

150 W television on 230 V. Calculate current and suggest fuse rating.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1167

3 kW electric cooker on 230 V. Calculate current and suggest circuit breaker rating.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1168

Ten 60 W lamps in parallel on 230 V lighting circuit. Total current and fuse rating.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1172

Same heater on 230 V. Calculate current.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1173

Suitable fuse rating for the immersion heater.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1176

Why transmit at high voltage?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1178

6×60W lamps + 2kW kettle + 1.5kW heater + 150W TV. Total power?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1179

Same appliances on 230 V. Total current?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1185

The correct fuse rating for an appliance should be __________ than the normal operating current.

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Completed

PHYSICS #1187

If a fault causes the case to become live, earthing causes a __________ current to flow, which blows the fuse.

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Completed

PHYSICS #1190

A __________ circuit forms a loop from the consumer unit around the house and back.

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Completed

PHYSICS #1073

What is the difference between heat capacity and specific heat capacity?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1075

Why is water's high specific heat capacity important for life?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1083

Why does steam at 100°C cause more severe burns than water at 100°C?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1086

Why is a calorimeter insulated?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1088

Why do coastal areas have milder climates than inland areas?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1089

Why is water used as a coolant in car radiators?

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Completed

PHYSICS #1091

A metal spoon and wooden spoon in a hot pot feel different. Why?

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Completed

PHYSICS #1093

Why does a large lake take longer to freeze than a small pond?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1094

In a specific heat capacity experiment, why transfer the hot metal quickly into the calorimeter?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1095

Why dry ice cubes before adding to a calorimeter?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1096

Why would a non-insulated calorimeter give inaccurate results?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1098

Heat required to raise 2 kg of water from 15°C to 35°C. (c_water = 4200 J/kg°C)

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1099

0.5 kg copper (c = 390 J/kg°C) heated from 20°C to 80°C. Heat absorbed?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1100

3 kg iron absorbs 54,000 J and temperature rises 40°C. Find c.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1101

1.5 kg aluminum (c = 900 J/kg°C) cools from 150°C to 30°C. Heat released?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1102

200 g metal requires 1800 J to rise 10°C. Find c.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1103

What mass of water heated from 20°C to 60°C by 84,000 J? (c = 4200 J/kg°C)

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1105

Heat needed to melt 3 kg of ice at 0°C. (L_f = 334,000 J/kg)

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1106

Heat released when 0.2 kg steam at 100°C condenses. (L_v = 2,260,000 J/kg)

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1130

When using a calorimeter, we must account for the heat absorbed by the __________ itself.

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Completed

PHYSICS #1007

Why must temperature be in Kelvin when using gas laws?

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Completed

PHYSICS #1016

What is the General Gas Equation for a fixed mass of gas?

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Completed

PHYSICS #1017

What is the Ideal Gas Equation?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1018

What is the approximate value of the universal gas constant R?

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Completed

PHYSICS #1019

What is absolute zero?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1021

Why does a balloon expand as it rises in the atmosphere?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1022

Why do aerosol cans warn against incineration or high temperatures?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1023

Why does pressure in a scuba tank decrease as air is used, even at constant temperature?

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Completed

PHYSICS #1024

Why does a bicycle pump get hot when inflating a tyre?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1025

Why does a sealed bottle of water crack in a freezer?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1026

Why is it dangerous to heat a sealed glass container containing a gas?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1027

What happens to car tyre pressure after a long drive, and why?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1030

Why do weather balloons expand as they rise and eventually burst?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1031

A gas occupies 600 cm³ at 80 kPa. What volume at 120 kPa, constant temperature?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1032

A gas has volume 2.5 L at 1.2 atm. Volume at 0.8 atm, constant temperature?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1033

A gas occupies 400 cm³ at 27°C. Volume at 87°C, constant pressure?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1035

Gas in rigid container at 150 kPa and 17°C. Pressure at 77°C?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1037

Gas at 27°C and 100 kPa heated to 127°C at constant volume. New pressure?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #1066

Equal volumes of gases at the same temperature and pressure contain equal numbers of __________.

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PHYSICS #945

What does a ticker-timer do?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #955

A ball thrown upwards: what are its velocity and acceleration at the very top?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #957

Can an object have constant speed but changing velocity? Give an example.

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PHYSICS #958

Can an object have zero velocity but non-zero acceleration? Give an example.

MEDIUM +30 XP 5 min

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PHYSICS #959

A car's speedometer reads a constant 60 km/h. Does this mean its velocity is constant?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #960

Why do a feather and hammer fall at the same rate on the Moon but not on Earth?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #966

A runner runs 400 m around a track in 50 seconds and returns to start. Find average speed and average velocity.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #969

A ticker-timer at 50 Hz has a 5-dot interval length 6 cm. Calculate velocity.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #974

A train at 30 m/s stops after 150 m. Find deceleration.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #975

For the same train (u=30 m/s, a=-3 m/s²), find time to stop.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #976

A ball thrown up with u=15 m/s (g=10 m/s²). Find maximum height.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #977

For the same ball, find time to reach maximum height.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #978

A stone is dropped and hits water after 2.5 s (g=10 m/s²). Find bridge height.

MEDIUM +30 XP 5 min

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Completed

PHYSICS #995

At the highest point of vertical motion, the velocity is , but the acceleration is still .

MEDIUM +30 XP 5 min

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Completed

PHYSICS #895

How can you find the poles of an unmarked bar magnet?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #897

How do iron filings map a magnetic field?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #901

How can you magnetize a steel bar by stroking?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #902

How can you magnetize a steel bar using an electric coil?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #906

What is a "hard" magnetic material?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #907

What is a "soft" magnetic material?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #908

Why is soft iron used for electromagnets?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #909

Why is steel used for permanent magnets?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #911

Why does a freely suspended magnet point north-south?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #914

Why does a compass needle point north?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #918

Why does heating a magnet cause it to lose magnetism?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #921

How does Earth's magnetic field protect us?

MEDIUM +30 XP 5 min

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PHYSICS #922

Why is magnetic declination important for ships and aircraft?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #932

How would you map the field of a horseshoe magnet?

MEDIUM +30 XP 5 min

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Completed

PHYSICS #935

Iron filings align along magnetic field lines because they become __________ magnets.

MEDIUM +30 XP 5 min

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PHYSICS #936

According to domain theory, an unmagnetized material has domains pointing in __________ directions.

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PHYSICS #940

The angle between geographic north and magnetic north is called __________.

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PHYSICS #853

What are the main parts of a vernier caliper?

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PHYSICS #854

What are the main parts of a micrometer screw gauge?

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PHYSICS #855

What is the purpose of the ratchet on a micrometer screw gauge?

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PHYSICS #856

What is a zero error in measuring instruments?

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PHYSICS #857

What is a positive zero error?

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PHYSICS #858

What is a negative zero error?

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PHYSICS #859

Which of these is a correct rule for significant figures?

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PHYSICS #865

A vernier caliper (LC=0.01 cm) shows main scale = 1.2 cm, vernier coincidence = 6. Calculate the reading.

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PHYSICS #866

Vernier caliper: main scale = 3.5 cm, vernier coincidence = 3, LC=0.01 cm. Find reading.

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PHYSICS #867

Vernier caliper: main scale = 0.8 cm, vernier coincidence = 9, LC=0.01 cm. Find reading.

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PHYSICS #868

Micrometer (LC=0.01 mm): main scale = 4.5 mm, thimble = 12. Calculate reading.

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PHYSICS #869

Micrometer: main scale = 7.0 mm, thimble = 38, LC=0.01 mm. Find reading.

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PHYSICS #870

Micrometer: main scale = 2.5 mm, thimble = 5, LC=0.01 mm. Find reading.

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PHYSICS #876

How many significant figures are in the number 100.0?

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PHYSICS #877

How many significant figures are in the number 0.00340?

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PHYSICS #878

How many significant figures are in 5.67 × 10⁵?

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PHYSICS #885

Convert 100 MW to watts.

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PHYSICS #886

A wire has diameter 0.56 mm. Express in metres using standard form.

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PHYSICS #887

Thickness = 2.3 × 10⁻⁵ m. Express in micrometres (µm).

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PHYSICS #814

Where is the centre of gravity of a triangular lamina?

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PHYSICS #815

How do you find the centre of gravity of an irregularly shaped piece of cardboard?

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PHYSICS #824

Why is a bus less likely to topple if luggage is stored in underfloor compartments rather than on a roof rack?

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PHYSICS #825

Why do racing cars have a very low profile and wide wheelbase?

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PHYSICS #826

What is meant by toppling?

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PHYSICS #829

Why do ships carry heavy cargo in their lower holds?

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PHYSICS #830

Why do you instinctively lower your centre of gravity when standing in a moving bus that suddenly brakes?

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PHYSICS #833

Why does a rugby player in a scrum adopt a low, wide stance?

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PHYSICS #834

A bottle of water is more stable when full than when empty. Why?

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PHYSICS #837

Why is it difficult to stand on one foot with your eyes closed?

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PHYSICS #845

To find the CoG of an irregular lamina, we use the __________ method.

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PHYSICS #850

An object topples when the line of action of its __________ falls outside its base.

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PHYSICS #762

What is the pole of a curved mirror?

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PHYSICS #763

What is the centre of curvature of a spherical mirror?

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PHYSICS #764

What is the radius of curvature of a spherical mirror?

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PHYSICS #765

What is the principal focus of a concave mirror?

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PHYSICS #766

What is the focal length of a spherical mirror?

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PHYSICS #770

Which of these is a rule for drawing ray diagrams for curved mirrors?

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PHYSICS #771

For a concave mirror, when the object is at infinity, the image is:

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PHYSICS #772

For a concave mirror, when the object is beyond C, the image is:

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PHYSICS #774

For a concave mirror, when the object is between C and F, the image is:

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PHYSICS #775

For a concave mirror, when the object is at F, what happens?

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PHYSICS #776

For a concave mirror, when the object is between F and P, the image is:

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PHYSICS #778

For a convex mirror, where is the image always located?

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PHYSICS #780

What is the mirror formula (Cartesian sign convention)?

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PHYSICS #781

What is the magnification formula for mirrors?

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PHYSICS #791

For the previous problem (u = -60, v = +20), find magnification.

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PHYSICS #797

For the rear-view mirror problem (u = -4, v = 1.33), find magnification.

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PHYSICS #808

A convex mirror always produces a , , and __ image.

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PHYSICS #810

Magnification m = -v/u. If m is positive, the image is __________.

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PHYSICS #711

What did Oersted's experiment demonstrate?

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PHYSICS #712

What is the magnetic field pattern around a straight current-carrying conductor?

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PHYSICS #713

For a straight conductor, the right-hand grip rule states that if you grip the wire with your right thumb pointing in the direction of __________, your fingers curl in the direction of the magnetic field.

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PHYSICS #716

How can you increase the strength of a solenoid's magnetic field?

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PHYSICS #717

For a solenoid, the right-hand grip rule states that if you curl your fingers in the direction of the current, your thumb points towards the __________ pole.

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PHYSICS #719

What does Fleming's Left-Hand Rule determine?

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PHYSICS #720

In Fleming's Left-Hand Rule, what does the first finger represent?

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PHYSICS #721

In Fleming's Left-Hand Rule, what does the thumb represent?

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PHYSICS #722

In Fleming's Left-Hand Rule, what does the second (centre) finger represent?

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PHYSICS #725

What are the main parts of a simple DC motor?

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PHYSICS #727

How can you increase the speed of a DC motor?

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PHYSICS #728

A compass needle is placed near a straight wire. What happens when current flows?

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PHYSICS #729

What happens to a compass needle when the current in a nearby wire is reversed?

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PHYSICS #732

When is the force on a current-carrying conductor in a magnetic field zero?

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PHYSICS #733

When is the force on a current-carrying conductor in a magnetic field maximum?

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PHYSICS #741

A wire 20 cm long is in a field of 0.4 T with current 5 A at 60° to the field. Calculate the force.

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PHYSICS #742

A force of 0.6 N acts on a conductor of length 0.3 m carrying 4 A perpendicular to a field. Calculate B.

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PHYSICS #743

A conductor 10 cm long experiences 0.15 N with 2 A perpendicular to the field. Find B.

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PHYSICS #744

A wire 25 cm long is at 30° to a 0.5 T field with current 6 A. Calculate the force.

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PHYSICS #746

Which of these increases the speed of a DC motor?

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PHYSICS #748

The force on a current-carrying conductor in a magnetic field is given by F = __________.

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PHYSICS #750

The magnetic field around a straight conductor consists of __________ circles.

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PHYSICS #752

The force on a current-carrying conductor in a magnetic field is given by __________ rule.

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PHYSICS #753

In an electric bell, the circuit is rapidly made and broken by the __________ screw.

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PHYSICS #756

The force on a conductor is maximum when it is __________ to the magnetic field.

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PHYSICS #757

For a straight conductor, if your right thumb points in the direction of __________, your fingers curl in the direction of the magnetic field.

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PHYSICS #619

What does amplitude tell us about a wave's energy?

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PHYSICS #626

Why does a floating cork bob up and down but not move horizontally as a wave passes?

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PHYSICS #628

Why can light travel through a vacuum but sound cannot?

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PHYSICS #630

Why does the pitch of an ambulance siren change as it passes you?

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PHYSICS #642

An earthquake P-wave travels at 8 km/s with frequency 2 Hz. Find wavelength in metres.

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PHYSICS #643

A radio wave has frequency 100 MHz (100 × 10⁶ Hz) and speed 3 × 10⁸ m/s. Find wavelength.

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PHYSICS #644

Wave crests pass every 4 seconds. Distance between crests is 8 m. Find wave speed.

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PHYSICS #649

Sound wave f=440 Hz, v=340 m/s. How many waves fit in 1 m?

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PHYSICS #650

Sonar echo returns after 2 seconds. v=1500 m/s. Find depth.

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PHYSICS #651

20 vibrations in 2.5 seconds, λ=0.5 m. Find frequency.

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PHYSICS #652

Same data (20 vibrations/2.5 s). Find period.

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PHYSICS #653

Same data (f=8 Hz, λ=0.5 m). Find speed.

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PHYSICS #655

Violin string f=256 Hz, v=320 m/s. Find wavelength on string.

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PHYSICS #656

Same note (256 Hz) in air at 340 m/s. Find wavelength.

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PHYSICS #526

What is the principle of moments?

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PHYSICS #527

What is meant by equilibrium in terms of moments?

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PHYSICS #528

What is a couple?

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PHYSICS #529

Which of these is an example of a couple?

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PHYSICS #530

Which of these is another example of a couple?

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PHYSICS #535

A see-saw has a pivot at its centre. A 300 N child sits 2 m from pivot on one side. Where must a 200 N child sit on the other side to balance?

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PHYSICS #536

A uniform metre rule pivoted at 50 cm. A 2 N weight at 20 cm, a 3 N weight at 70 cm. Is it balanced?

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PHYSICS #541

A wheel of diameter 0.8 m has a rope wrapped around its rim. A force of 50 N is applied to the rope. Calculate the turning moment.

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PHYSICS #543

A crowbar: pivot 0.2 m from stone, effort applied 1 m from pivot. Stone exerts 600 N downward. What effort to just lift? (Crowbar light)

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PHYSICS #544

A non-uniform rod weight 40 N, length 3 m, balances at a point 1.2 m from one end. Where is the centre of gravity?

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PHYSICS #555

A __________ is a pair of equal and opposite parallel forces not in the same line.

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PHYSICS #560

Why is it easier to hold a weight close to your body than at arm's length?

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PHYSICS #561

In a wheelbarrow, the load is placed near the wheel. Why?

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PHYSICS #417

What happens when a polythene rod is rubbed with wool?

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PHYSICS #418

What happens when a glass rod is rubbed with silk?

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PHYSICS #419

What is the difference between charging by contact and charging by induction?

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PHYSICS #420

What are the three main uses of a gold-leaf electroscope?

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PHYSICS #422

How does a lightning conductor protect a building?

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PHYSICS #423

Why does a plastic comb attract small pieces of paper after being used on dry hair?

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PHYSICS #424

Why can a metal rod not be charged by friction if held in the hand?

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PHYSICS #425

A negatively charged electroscope is brought near a negatively charged rod. What happens to the leaf?

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PHYSICS #426

A negatively charged electroscope is brought near a positively charged rod. What happens to the leaf?

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PHYSICS #429

A charged object is brought near a neutral electroscope. The leaf diverges. Why?

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PHYSICS #433

What would happen if a lightning conductor was not properly earthed?

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PHYSICS #435

Why do fuel tankers often drag a metal chain on the ground?

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PHYSICS #438

Two identical metal spheres: A positive, B neutral. They are touched then separated. Final charges?

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PHYSICS #444

How can a charged electroscope test if a material is a conductor or insulator?

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PHYSICS #452

Charging without contact is called charging by __________.

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PHYSICS #453

The gold-leaf electroscope is used to , , and __ charge.

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PHYSICS #454

If leaf divergence increases when a test charge is brought near, the test charge is __________.

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PHYSICS #294

Why are metals good conductors of heat?

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PHYSICS #295

Why is air a poor conductor of heat?

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PHYSICS #297

Which of these affects the rate of heat transfer by conduction through a solid?

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PHYSICS #298

What is a convection current?

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PHYSICS #300

How does thermal radiation differ from conduction and convection?

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PHYSICS #302

Why is the collector plate in a solar water heater painted dull black?

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PHYSICS #303

What features of a vacuum flask reduce heat transfer?

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PHYSICS #307

How does a woollen blanket keep us warm in winter?

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PHYSICS #309

Is the statement "Heat rises" scientifically accurate?

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PHYSICS #310

Why are heaters placed near the floor but air conditioners high on walls?

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PHYSICS #311

Why is a fridge more efficient when its cooling fins are clean and well ventilated?

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PHYSICS #313

Why does a hot drink cool faster in a metal cup than in a ceramic cup?

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PHYSICS #315

Why do we feel colder on a windy day than on a calm day at the same temperature?

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PHYSICS #316

How can birds soar to great heights without flapping their wings?

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PHYSICS #317

Why is the heating element of an electric kettle placed at the bottom?

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PHYSICS #318

How can you compare the thermal conductivity of different metals experimentally?

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PHYSICS #319

How can you demonstrate convection currents in a liquid?

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PHYSICS #321

Design an experiment to compare absorption of dull black vs shiny white surfaces.

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PHYSICS #327

How does a vacuum flask keep cold liquids cold?

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PHYSICS #329

How does a fireplace help ventilate a room?

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PHYSICS #332

Metals are good conductors because they have __________ electrons.

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PHYSICS #337

The __________ in a flask prevents heat transfer by conduction and convection.

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PHYSICS #338

The __________ walls in a flask reduce heat loss by radiation.

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PHYSICS #339

The __________ stopper in a flask is a poor conductor, so it reduces conduction.

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PHYSICS #341

What does a thermal imaging camera detect?

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PHYSICS #344

Why do draughts (drafts) increase heat loss from a room?

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PHYSICS #347

Why do laptops have cooling fans and vents?

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PHYSICS #350

How does a greenhouse keep plants warm in winter?

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PHYSICS #249

What causes convection currents in a fluid?

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PHYSICS #251

Which surface is the best absorber of thermal radiation?

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PHYSICS #252

Which surface is the best emitter of thermal radiation?

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PHYSICS #253

Which surface is the best reflector of thermal radiation?

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PHYSICS #254

Why does a metal spoon feel colder than a wooden spoon at the same room temperature?

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PHYSICS #257

Why are room heaters usually placed near the floor?

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PHYSICS #258

Why is the freezer compartment in a refrigerator usually at the top?

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PHYSICS #263

Why do double-glazed windows reduce heat loss from a house?

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PHYSICS #264

How does cavity wall insulation reduce heat loss?

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PHYSICS #266

Why are household radiators often painted with dull, matt paint rather than shiny metallic paint?

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PHYSICS #267

How does a chimney work to remove smoke?

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PHYSICS #268

Why does an ice cube melt faster on a metal surface than on a wooden surface at the same temperature?

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PHYSICS #269

A drink cools faster when you blow on it. Why?

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PHYSICS #271

How would you compare the thermal conductivity of different metals experimentally?

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PHYSICS #272

How can you demonstrate convection in water?

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PHYSICS #274

What is the main difference between conduction and convection?

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PHYSICS #275

What is the main difference between convection and radiation?

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PHYSICS #276

Why are metals better conductors than non-metals?

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PHYSICS #277

A solar water heater panel is painted black. Why?

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PHYSICS #288

A __________ black surface is the best absorber of thermal radiation.

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PHYSICS #289

A __________ shiny surface is the best reflector of thermal radiation.

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PHYSICS #181

Why do most substances expand when heated?

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PHYSICS #183

What three factors affect how much a solid rod expands when heated?

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PHYSICS #185

What happens when a bimetallic strip is heated?

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PHYSICS #186

What happens when a bimetallic strip is cooled?

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PHYSICS #189

Why is one end of a long bridge mounted on rollers?

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PHYSICS #191

Which liquid expands more for the same temperature rise?

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PHYSICS #194

At what temperature does water have its maximum density?

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PHYSICS #196

Why can fish survive in a frozen pond in winter?

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PHYSICS #197

What does Charles's Law state?

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PHYSICS #198

What is the mathematical expression for Charles's Law?

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PHYSICS #201

Why does running hot water over a tight metal lid on a glass jar loosen it?

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PHYSICS #204

Why must the two metals in a bimetallic thermostat have different coefficients of expansion?

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PHYSICS #206

Why do water pipes burst in winter when water freezes?

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PHYSICS #207

Why can a flask with a stopper and narrow tube be used as a simple thermometer?

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PHYSICS #208

A flask filled to the brim with water, sealed tightly, is placed in a freezer. What happens?

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PHYSICS #209

Why do hot water heaters have expansion pipes or safety valves?

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PHYSICS #213

A steel bridge is 100 m long at 5°C. How much longer at 35°C? (α_steel = 0.000012/°C)

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PHYSICS #214

A brass rod (1.0 m) increases by 0.6 mm when heated through 50°C. Calculate α for brass.

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PHYSICS #215

An iron rail is 20.000 m at 10°C. Length at 40°C? (α_iron = 0.000012/°C)

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PHYSICS #219

A gas has volume 300 cm³ at 27°C. Volume at 127°C? (Pressure constant)

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PHYSICS #221

Gas volume 60 cm³ at 27°C. Volume at 127°C? (Pressure constant)

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PHYSICS #225

In a Charles's Law experiment with a syringe, why must pressure be kept constant?

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PHYSICS #231

Alcohol expands __________ than mercury for the same temperature rise.

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PHYSICS #234

Charles's law states that volume is directly proportional to __________ temperature.

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PHYSICS #235

The apparatus used to demonstrate anomalous expansion of water is __________ apparatus.

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Completed

PHYSICS #238

Why is a narrower capillary tube more sensitive in a liquid thermometer?

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PHYSICS #240

What is absolute zero?

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PHYSICS #137

What is Brownian motion?

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PHYSICS #138

What causes smoke particles in a smoke cell to move in a random zig-zag path?

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PHYSICS #139

How does an increase in temperature affect Brownian motion?

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PHYSICS #144

Why does a gas diffuse faster than a liquid?

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PHYSICS #149

Why does a gas fill its container completely?

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PHYSICS #153

Which of these is an example of cohesion?

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PHYSICS #154

Which of these is an example of adhesion?

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PHYSICS #155

What is surface tension?

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PHYSICS #156

Why can a steel needle float on water even though steel is denser than water?

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PHYSICS #157

How can a water strider insect walk on the surface of a pond?

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PHYSICS #167

When a balloon is inflated, the air pushes outwards on the rubber. Why?

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PHYSICS #168

A student says: "Particles in a solid are not moving." Is this correct?

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PHYSICS #171

In the smoke cell experiment, what would you observe if the air was heated?

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PHYSICS #175

Why does water form droplets on a waxed car surface but spread on clean glass?

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PHYSICS #178

How does Brownian motion support the Kinetic Theory of matter?

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PHYSICS #126

What is standard atmospheric pressure (1 atm) in pascals?

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PHYSICS #128

What is the difference between gauge pressure and absolute pressure?

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PHYSICS #078

Why does a sharp knife cut better than a blunt one?

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Completed

PHYSICS #082

What is the formula for pressure at a depth in a liquid?

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PHYSICS #083

Which of these is a characteristic of liquid pressure?

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PHYSICS #084

Liquid pressure at a given depth depends on which of these?

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Completed

PHYSICS #085

What does Pascal's principle state?

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PHYSICS #087

What principle do hydraulic brakes use?

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PHYSICS #088

What does the Magdeburg hemispheres experiment demonstrate?

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PHYSICS #090

In a mercury barometer, what supports the mercury column?

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PHYSICS #091

Why does atmospheric pressure decrease with altitude?

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PHYSICS #093

What is a practical use of a siphon?

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PHYSICS #094

In a hydraulic jack, if the large piston has 10× the area of the small piston, what is the force multiplication factor?

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PHYSICS #098

A concrete block has dimensions 0.5 m × 0.3 m × 0.2 m, density 2500 kg/m³. Calculate its mass.

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PHYSICS #100

The block (weight 750 N) rests on its largest face (0.5 m × 0.3 m). Calculate pressure.

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PHYSICS #101

The block (weight 750 N) rests on its smallest face (0.3 m × 0.2 m). Calculate pressure.

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PHYSICS #102

Calculate the pressure at a depth of 5 m in a swimming pool. (ρ = 1000 kg/m³, g = 10 N/kg)

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Completed

PHYSICS #105

In a hydraulic system, small piston area = 0.01 m², large piston area = 0.5 m². Force on small piston = 200 N. Calculate pressure transmitted.

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PHYSICS #106

Using the same system (P = 20,000 Pa, large area = 0.5 m²), what force does the large piston exert?

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PHYSICS #108

At sea level, mercury barometer reads 760 mm. ρ_Hg = 13,600 kg/m³, g = 10 N/kg. Calculate atmospheric pressure in Pa.

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PHYSICS #111

A card stays on an upside-down glass of water. Why?

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PHYSICS #114

A U-tube can compare densities of immiscible liquids. What is measured?

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PHYSICS #117

Why do mountaineers sometimes get nosebleeds at high altitude?

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PHYSICS #118

Why is it harder to suck a drink through a straw on a high mountain?

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PHYSICS #123

When using a bicycle pump, what energy conversion occurs?

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PHYSICS #124

If you dive to 20 m depth in water, the pressure is approximately how many times atmospheric pressure? (Assume 10 m water = 1 atm)

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PHYSICS #073

A Eureka can overflows 30 cm³ of water when an object is immersed. The object has mass 240 g. What is its density?

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PHYSICS #075

A measurement is recorded as 2.50 cm. How many significant figures does it have?

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PHYSICS #040

A rectangular block has length 5 cm, width 4 cm, height 2 cm, and mass 80 g. Calculate its density in g/cm³.

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PHYSICS #042

An irregular solid has mass 120 g. When immersed in water, water level rises from 30 cm³ to 50 cm³. Calculate density.

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Completed

PHYSICS #043

An irregular stone has mass 250 g. When placed in a measuring cylinder with 100 cm³ water, water rises to 140 cm³. Calculate density in g/cm³.

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Completed

PHYSICS #044

A substance has density 8 g/cm³ and mass 240 g. What is its volume?

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PHYSICS #045

A liquid has density 0.8 g/cm³ and volume 50 cm³. What is its mass?

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Completed

PHYSICS #046

An object floats in water. What can you conclude about its density?

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Completed

PHYSICS #050

What is a Eureka (displacement) can used for?

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PHYSICS #051

What is the least count (accuracy) of a typical vernier caliper?

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PHYSICS #052

What is the least count (accuracy) of a typical micrometer screw gauge?

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PHYSICS #056

What is a zero error in measuring instruments?

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PHYSICS #057

What is parallax error?

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PHYSICS #060

How would you measure the area of an irregular leaf?

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Completed

PHYSICS #061

Why is an astronaut's mass the same on Earth and the Moon?

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Completed

PHYSICS #063

If a person weighs 600 N on Earth (g = 10 N/kg), what is their weight on the Moon (g = 1.6 N/kg)?

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Completed

PHYSICS #065

Why is it important to take the average of several readings?

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Completed

PHYSICS #067

How can you reduce error when measuring the period of a pendulum?

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Completed

PHYSICS #069

Convert 100 cm³ to m³.

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Completed

PHYSICS #003

Why does an astronaut's weight change on the Moon but their mass remains the same?

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PHYSICS #005

If forces acting on an object are balanced, what can be said about its motion?

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Completed

PHYSICS #007

What is the mathematical formula for Hooke's Law?

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PHYSICS #008

What happens if a spring is stretched beyond its elastic limit?

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PHYSICS #009

Which method is most effective for reducing friction between moving machine parts?

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PHYSICS #011

A person weighs 600 N on Earth (g = 10 N/kg). What is their mass? What would they weigh on the Moon where g = 1.6 N/kg?

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Completed

PHYSICS #014

A car experiences a forward force of 500 N from its engine and a total frictional force of 350 N. What is the resultant force?

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PHYSICS #015

Three forces act on a point: 10 N east, 6 N west, and 8 N east. Calculate the net force.

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PHYSICS #016

A spring stretches by 0.05 m when a force of 10 N is applied. Calculate the spring constant (k).

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PHYSICS #017

What force is needed to stretch a spring with a spring constant of 200 N/m by 0.15 m?

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PHYSICS #019

A spring has a spring constant of 50 N/m. It is stretched until its length is 22 cm. Its original length was 20 cm. Calculate the force applied.

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Completed

PHYSICS #021

A car is travelling at a constant speed of 20 m/s on a straight, level road. Why is the car not accelerating?

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Completed

PHYSICS #023

Why do vehicle tyres have tread patterns?

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PHYSICS #024

Why do weightlifters use chalk powder (magnesium carbonate) on their hands?

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Completed

CHEMISTRY #3682

List three physical properties of chlorine.

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CHEMISTRY #3683

Write the equation for the reaction of chlorine with sodium.

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Completed

CHEMISTRY #3684

Write the equation for the reaction of chlorine with hydrogen.

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Completed

CHEMISTRY #3686

Write the equation for the reaction of chlorine with potassium iodide solution.

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Completed

CHEMISTRY #3689

Why is hydrogen chloride gas not collected over water?

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Completed

CHEMISTRY #3691

Write the equation for the reaction of hydrochloric acid with magnesium.

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Completed

CHEMISTRY #3692

Write the equation for the reaction of hydrochloric acid with sodium carbonate.

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Completed

CHEMISTRY #3693

Write the equation for the reaction of hydrochloric acid with sodium hydroxide.

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Completed

CHEMISTRY #3695

Give two uses of chlorine and two uses of hydrochloric acid.

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Completed

CHEMISTRY #3706

Chlorine is a -yellow gas with a odor.

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Completed

CHEMISTRY #3709

Hydrogen chloride gas is (more/less) dense than air and soluble in water.

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Completed

CHEMISTRY #3710

Dry HCl gas does not turn litmus paper because it contains no __________ ions.

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Completed

CHEMISTRY #3711

When HCl gas meets ammonia gas, dense white fumes of __________ are formed.

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Completed

CHEMISTRY #3719

Write equation for reaction of HCl with ammonia.

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Completed

CHEMISTRY #3734

The reactivity of halogens __________ down Group VII.

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Completed

CHEMISTRY #3735

Chlorine is a powerful __________ agent because it readily gains an electron.

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Completed

CHEMISTRY #3736

Bromine dissolved in an organic solvent appears __________ in color.

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CHEMISTRY #3737

Iodine dissolved in an organic solvent appears __________ in color.

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CHEMISTRY #3744

How would you test for chloride ion in solution?

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Completed

CHEMISTRY #3755

The hypochlorite ion has the formula __________.

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Completed

CHEMISTRY #3756

The chlorate ion has the formula __________.

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Completed

CHEMISTRY #3757

The perchlorate ion has the formula __________.

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Completed

CHEMISTRY #3764

List three physical properties of sulphur dioxide.

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Completed

CHEMISTRY #3767

Write the overall equation for the Contact Process step where SO₂ is converted to SO₃.

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Completed

CHEMISTRY #3770

Give two uses of concentrated sulphuric acid as a dehydrating agent and as an oxidizing agent.

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Completed

CHEMISTRY #3781

The Frasch process uses __________ water to melt sulphur underground.

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Completed

CHEMISTRY #3782

Rhombic sulphur is stable below __________°C.

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Completed

CHEMISTRY #3783

Sulphur dioxide is an oxide and turns moist litmus .

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Completed

CHEMISTRY #3787

Concentrated sulphuric acid reacts with copper to produce __________ gas.

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Completed

CHEMISTRY #3788

Sulphuric acid is a __________ acid, meaning it can form both sulfates and hydrogen sulfates.

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Completed

CHEMISTRY #3789

Write equation for burning of sulphur in air.

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Completed

CHEMISTRY #3790

Write equation for reaction of sodium sulphite with dilute hydrochloric acid.

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Completed

CHEMISTRY #3793

Write equation for oxidation of SO₂ to SO₃ (Contact Process).

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Completed

CHEMISTRY #3812

The gas with a rotten egg smell is .

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Completed

CHEMISTRY #3816

Sulphur burns in air with a __________ flame.

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Completed

CHEMISTRY #3581

Define exothermic and endothermic reactions. Give two examples of each.

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Completed

CHEMISTRY #3582

What is meant by ΔH? What does a positive and negative ΔH indicate?

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Completed

CHEMISTRY #3584

What is the effect of a catalyst on an energy level diagram?

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Completed

CHEMISTRY #3587

Why is the standard enthalpy of formation of an element in its standard state zero?

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Completed

CHEMISTRY #3601

In an exothermic reaction, the enthalpy of the products is __________ than that of the reactants.

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Completed

CHEMISTRY #3602

The activation energy is the minimum energy required for a reaction to __________.

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Completed

CHEMISTRY #3603

A catalyst lowers the energy but does not change the overall .

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Completed

CHEMISTRY #3604

Hess's Law is a consequence of enthalpy being a __________ function.

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CHEMISTRY #3605

The standard enthalpy change of formation of an element in its standard state is __________.

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CHEMISTRY #3607

Hydration energy is always __________ (exothermic/endothermic).

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Completed

CHEMISTRY #3620

Define bond dissociation energy.

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CHEMISTRY #3622

The average energy required to break a covalent bond is called energy.

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Completed

CHEMISTRY #3623

The measurement of heat changes in chemical reactions is called __________.

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CHEMISTRY #3626

Standard enthalpy changes are measured at bar pressure and usually K.

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Completed

CHEMISTRY #3627

Complete combustion of a hydrocarbon produces and .

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CHEMISTRY #3629

For a reaction aA + bB → cC + dD, ΔH°rxn = ΣcΔH°f(C) + dΔH°f(D) - [__________].

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Completed

CHEMISTRY #3632

A catalyst affects the (rate) of a reaction but not the (ΔH).

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CHEMISTRY #3635

Lattice energy becomes __________ (more negative/less negative) as ionic radius increases.

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CHEMISTRY #3636

Hydration energy becomes __________ (more negative/less negative) as ion size decreases.

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Completed

CHEMISTRY #3637

In an energy level diagram, the vertical axis represents __________.

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CHEMISTRY #3638

Activation energy is the minimum energy required for __________ to react.

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Completed

CHEMISTRY #3640

Enthalpy, internal energy, and entropy are examples of __________ functions.

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CHEMISTRY #3641

Hess's Law allows calculation of ΔH for reactions that are difficult to measure __________.

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Completed

CHEMISTRY #3643

Bond energies are usually expressed in __________ per mole.

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CHEMISTRY #3644

In exothermic reactions, the products are more __________ (lower energy) than the reactants.

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Completed

CHEMISTRY #3645

In endothermic reactions, the products are __________ (higher energy) than the reactants.

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Completed

CHEMISTRY #3647

One kilojoule (kJ) equals __________ joules.

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Completed

CHEMISTRY #3648

1 calorie (cal) = __________ joules.

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Completed

CHEMISTRY #3649

Calculate heat needed to raise 100 g water from 20°C to 30°C. (c = 4.18 J/g°C)

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Completed

CHEMISTRY #3650

The specific heat capacity of water is approximately __________ J/g°C.

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Completed

CHEMISTRY #3652

An exothermic reaction has a __________ ΔH.

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Completed

CHEMISTRY #3653

An endothermic reaction has a __________ ΔH.

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Completed

CHEMISTRY #3654

Write the formation reaction for water (H₂O).

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Completed

CHEMISTRY #3655

Write the combustion reaction for methane (CH₄).

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Completed

CHEMISTRY #3657

Lattice energy is always __________ (exothermic/endothermic).

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CHEMISTRY #3658

Hydration energy is always __________ (exothermic/endothermic).

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CHEMISTRY #3660

Ionization energy is always __________ (exothermic/endothermic).

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CHEMISTRY #3663

Compounds with low melting points often have __________ (molecular/ionic) lattice structures.

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Completed

CHEMISTRY #3664

Compounds with high melting points often have __________ (ionic/covalent network) lattice structures.

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CHEMISTRY #3671

The enthalpy change when 1 mole of H⁺ reacts with 1 mole of OH⁻ to form 1 mole of H₂O is called enthalpy of __________.

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Completed

CHEMISTRY #3674

The study of energy changes in chemical reactions is called __________.

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Completed

CHEMISTRY #3675

Name an endothermic reaction used in instant cold packs.

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CHEMISTRY #3676

Name an exothermic reaction used in hand warmers.

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Completed

CHEMISTRY #3677

In thermochemistry, the symbol Δ represents __________.

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Completed

CHEMISTRY #3678

Using Hess's Law, ΔH°rxn = ΣΔH°f(products) - ΣΔH°f(__________).

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Completed

CHEMISTRY #3679

The symbol ΔH° indicates a standard enthalpy change measured under __________ conditions.

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Completed

CHEMISTRY #3680

The SI unit for enthalpy change is __________.

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Completed

CHEMISTRY #3562

State Avogadro's law.

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Completed

CHEMISTRY #3563

What are the standard temperature and pressure (STP) conditions?

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CHEMISTRY #3564

What are room temperature and pressure (RTP) conditions?

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CHEMISTRY #3565

What volume does 1 mole of any ideal gas occupy at STP?

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Completed

CHEMISTRY #3566

What volume does 1 mole of any ideal gas occupy at RTP (25°C, 1 atm)?

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Completed

CHEMISTRY #3567

The ideal gas equation is __________.

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Completed

CHEMISTRY #3575

Dalton's law of partial pressures states that total pressure is sum of __________ pressures.

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CHEMISTRY #3576

Air is 21% O₂ and 79% N₂ by volume. If total pressure is 1 atm, what is partial pressure of O₂?

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Completed

CHEMISTRY #3577

One atmosphere (atm) is equal to mmHg and kPa.

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Completed

CHEMISTRY #3578

Boyle's law experiment requires that __________ and amount of gas are constant.

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CHEMISTRY #3579

Charles's law requires that __________ and amount of gas are constant.

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Completed

CHEMISTRY #3580

Which gas law describes the relationship between pressure and volume? Between volume and temperature?

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Completed

CHEMISTRY #3521

State Boyle's law. Write its mathematical form.

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Completed

CHEMISTRY #3523

Write the equation for the combined gas law.

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Completed

CHEMISTRY #3525

What is absolute zero? Why is it important in gas laws?

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Completed

CHEMISTRY #3526

If the pressure on a gas is doubled (at constant temperature), what happens to its volume?

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Completed

CHEMISTRY #3527

If the temperature of a gas is doubled (in Kelvin, at constant pressure), what happens to its volume?

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Completed

CHEMISTRY #3530

Explain why a balloon inflated with air shrinks when placed in a freezer (Charles's law).

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Completed

CHEMISTRY #3531

A syringe is filled with air and the outlet is sealed. If you push the plunger in, you feel increasing resistance. Explain why.

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Completed

CHEMISTRY #3534

Two gases, hydrogen and carbon dioxide, are released at the same time at one end of a room. Which gas will reach the other end first? Why?

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Completed

CHEMISTRY #3537

Boyle's law states that pressure is __________ proportional to volume at constant temperature.

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Completed

CHEMISTRY #3538

Charles's law states that volume is directly proportional to __________ temperature.

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Completed

CHEMISTRY #3539

The combined gas law equation is __________ = constant.

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CHEMISTRY #3540

Graham's law states that the rate of diffusion is inversely proportional to the __________ of the molar mass.

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Completed

CHEMISTRY #3541

At constant temperature, if volume increases, pressure __________.

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CHEMISTRY #3542

At constant pressure, if Kelvin temperature increases, volume __________.

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Completed

CHEMISTRY #3543

The slowest diffusing gas among H₂, He, O₂, and CO₂ is likely __________.

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Completed

CHEMISTRY #3544

A gas occupies 600 mL at 80 kPa. What volume at 120 kPa, temperature constant?

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Completed

CHEMISTRY #3451

Define allotropes. Name two allotropes of carbon.

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Completed

CHEMISTRY #3453

Explain why diamond is very hard and graphite is soft.

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Completed

CHEMISTRY #3455

Give two uses of diamond and two uses of graphite.

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Completed

CHEMISTRY #3456

How is carbon dioxide prepared in the laboratory? Write the equation.

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Completed

CHEMISTRY #3457

What is the chemical test for carbon dioxide gas? Describe the observation.

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Completed

CHEMISTRY #3460

Why is carbon monoxide poisonous?

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Completed

CHEMISTRY #3461

Write the equation for the burning of carbon monoxide.

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Completed

CHEMISTRY #3463

What happens when copper carbonate is heated? Write the equation.

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Completed

CHEMISTRY #3465

Name two human activities that increase atmospheric CO₂.

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Completed

CHEMISTRY #3477

A sample of gas is colourless and odourless. It extinguishes a burning splint. When bubbled through limewater, it turns milky. Identify the gas.

EASY +15 XP 5 min

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Completed

CHEMISTRY #3478

Another gas is colourless and odourless, burns with a blue flame, and is very toxic. Identify it.

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Completed

CHEMISTRY #3479

Diamond and graphite are __________ of carbon.

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Completed

CHEMISTRY #3480

In diamond, each carbon atom is bonded to __________ other carbon atoms.

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Completed

CHEMISTRY #3481

Graphite conducts electricity because it has __________ electrons.

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Completed

CHEMISTRY #3482

Carbon dioxide is prepared in the lab by reacting with acid.

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Completed

CHEMISTRY #3483

The test for CO₂ is that it turns __________ milky.

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Completed

CHEMISTRY #3484

Carbon monoxide burns with a __________ flame.

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Completed

CHEMISTRY #3485

CO is highly toxic because it combines with __________ in the blood.

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Completed

CHEMISTRY #3486

Most carbonates on heating to give the metal oxide and .

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Completed

CHEMISTRY #3487

The process by which plants absorb CO₂ to make food is called __________.

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Completed

CHEMISTRY #3488

Write balanced equation for complete combustion of carbon to CO₂.

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Completed

CHEMISTRY #3489

Write balanced equation for incomplete combustion of carbon to CO.

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Completed

CHEMISTRY #3490

Write equation for reaction of sodium carbonate with hydrochloric acid.

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Completed

CHEMISTRY #3491

Write equation for thermal decomposition of calcium carbonate.

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Completed

CHEMISTRY #3493

Write equation for burning of methane (CH₄) in excess oxygen.

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Completed

CHEMISTRY #3507

Solid carbon dioxide is called .

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Completed

CHEMISTRY #3508

Carbon dioxide is an __________ oxide because it dissolves in water to form carbonic acid.

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Completed

CHEMISTRY #3517

A process that releases no net CO₂ (captures as much as it emits) is called -.

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Completed

CHEMISTRY #3518

The total greenhouse gas emissions caused by an individual, event, or product is called its .

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Completed

CHEMISTRY #3381

Define an electrolyte. Give two examples.

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Completed

CHEMISTRY #3382

Explain why solid sodium chloride does not conduct electricity, but molten sodium chloride does.

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Completed

CHEMISTRY #3383

Name the two electrodes in electrolysis. Which one is positive, and which one is negative?

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Completed

CHEMISTRY #3384

What is meant by the term "electrolysis"?

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Completed

CHEMISTRY #3387

What is electroplating? Give one reason for electroplating an object.

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Completed

CHEMISTRY #3391

Explain why copper sulfate solution conducts electricity, but sugar solution does not.

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Completed

CHEMISTRY #3401

Ionic compounds conduct electricity when or .

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Completed

CHEMISTRY #3402

The electrode is positive and attracts ions.

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Completed

CHEMISTRY #3403

Oxidation occurs at the , reduction occurs at the .

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Completed

CHEMISTRY #3404

During electrolysis of molten lead(II) bromide, is formed at the cathode and gas is formed at the anode.

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Completed

CHEMISTRY #3405

In electroplating, the object to be plated is made the __________ electrode.

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Completed

CHEMISTRY #3406

Aluminium is extracted from its ore, __________, by electrolysis.

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Completed

CHEMISTRY #3408

In the electrolysis of water, gas is produced at the cathode and gas at the anode.

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Completed

CHEMISTRY #3409

Write half-equation for formation of magnesium metal at the cathode during electrolysis of molten MgCl₂.

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Completed

CHEMISTRY #3410

Write half-equation for formation of iodine at the anode during electrolysis of molten potassium iodide.

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Completed

CHEMISTRY #3412

Write half-equation for formation of chlorine gas at the anode from chloride ions.

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Completed

CHEMISTRY #3413

Write half-equation for deposition of silver at the cathode during electroplating.

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Completed

CHEMISTRY #3416

Write the overall equation for electrolysis of molten lead(II) bromide.

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Completed

CHEMISTRY #3417

Write the overall equation for electrolysis of water (dilute sulfuric acid).

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Completed

CHEMISTRY #3431

During electrolysis of CuSO₄ with copper electrodes, the anode mass and the cathode mass.

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Completed

CHEMISTRY #3438

What gas is produced at each electrode during electrolysis of dilute sulfuric acid with platinum electrodes?

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Completed

CHEMISTRY #3439

How can you test that the gas produced at the cathode during water electrolysis is hydrogen?

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Completed

CHEMISTRY #3440

How can you test that the gas produced at the anode during water electrolysis is oxygen?

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Completed

CHEMISTRY #3212

Why is a sodium ion (Na⁺) smaller than a sodium atom (Na)?

EASY +15 XP 5 min

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Completed

CHEMISTRY #3213

Why is a chloride ion (Cl⁻) larger than a chlorine atom (Cl)?

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Completed

CHEMISTRY #3214

Define first ionization energy.

EASY +15 XP 5 min

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Completed

CHEMISTRY #3216

Define electronegativity. Which element in Period 3 has the highest electronegativity and why?

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Completed

CHEMISTRY #3218

State the trend in metallic character across a period.

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Completed

CHEMISTRY #3219

Explain why the atomic radius of magnesium is smaller than that of sodium, even though magnesium has more protons and electrons.

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Completed

CHEMISTRY #3225

Based on periodic trends, predict whether strontium (Sr, below calcium) will have higher or lower ionization energy than calcium. Explain.

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Completed

CHEMISTRY #3226

Why does sodium (metal) have low electronegativity while chlorine (non-metal) has high electronegativity?

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Completed

CHEMISTRY #3227

Atom X has smaller atomic radius than atom Y, both in same period. Which has higher ionization energy?

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Completed

CHEMISTRY #3229

Across a period, atomic radius due to increasing charge.

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Completed

CHEMISTRY #3230

A positive ion (cation) is __________ than its parent atom because it has lost its outer shell.

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Completed

CHEMISTRY #3231

Ionization energy is the energy required to remove an electron from a __________ atom.

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Completed

CHEMISTRY #3232

The general trend for first ionization energy across a period is to __________.

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Completed

CHEMISTRY #3233

Electronegativity is a measure of an atom's ability to __________ a shared pair of electrons.

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Completed

CHEMISTRY #3234

The element with the highest electronegativity in the Periodic Table is __________.

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Completed

CHEMISTRY #3235

Down a group, electronegativity because atomic radius .

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Completed

CHEMISTRY #3250

State the trend in atomic radius down a group. Explain.

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Completed

CHEMISTRY #3251

State the trend in first ionization energy down a group. Explain.

EASY +15 XP 5 min

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Completed

CHEMISTRY #3254

Which element in Period 3 has the largest atomic radius?

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Completed

CHEMISTRY #3257

Why are noble gases unreactive (inert)?

EASY +15 XP 5 min

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Completed

CHEMISTRY #3258

Ionization energy is usually expressed in or per mole.

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Completed

CHEMISTRY #3259

Among halogens (F, Cl, Br, I), __________ has the highest electronegativity.

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Completed

CHEMISTRY #3260

Among alkali metals (Li, Na, K, Rb, Cs), __________ has the lowest ionization energy.

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Completed

CHEMISTRY #3261

Group I elements have ionization energies because they have valence electron(s).

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Completed

CHEMISTRY #3262

Group VII (halogens) have ionization energies because they have valence electrons.

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Completed

CHEMISTRY #3273

Order Li, Na, K by increasing atomic radius.

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Completed

CHEMISTRY #3274

Order F, Cl, Br by increasing atomic radius.

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Completed

CHEMISTRY #3275

Order F, Cl, Br by increasing electronegativity.

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Completed

CHEMISTRY #3276

Order Ca and Ba by increasing first ionization energy.

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Completed

CHEMISTRY #3277

The largest atom in Group I is __________.

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Completed

CHEMISTRY #3278

The smallest atom among halogens is __________.

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Completed

CHEMISTRY #3279

The most electronegative element in the periodic table is __________.

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Completed

CHEMISTRY #3280

Atoms tend to gain, lose, or share electrons to achieve a stable __________ electrons in their outer shell.

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Completed

CHEMISTRY #3285

What is the difference between a group and a period?

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Completed

CHEMISTRY #3286

How many valence electrons do Group I elements have?

EASY +15 XP 5 min

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Completed

CHEMISTRY #3287

How many valence electrons do Group VII elements have?

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Completed

CHEMISTRY #3288

What electron configuration do noble gases have?

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Completed

CHEMISTRY #3289

The period number of an element equals the number of __________.

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Completed

CHEMISTRY #3290

For main group elements, the group number often equals the number of __________ electrons.

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Completed

CHEMISTRY #3294

Elements with properties intermediate between metals and non-metals are called __________.

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Completed

CHEMISTRY #3295

Boron (B) is a __________, located on the boundary between metals and non-metals.

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Completed

CHEMISTRY #3300

Complete this sentence: As you move from left to right across a period, atomic radius , ionization energy , and electronegativity __.

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Completed

CHEMISTRY #3121

Define ionic bonding. Between which types of elements does it occur?

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Completed

CHEMISTRY #3122

Describe what happens to the electrons when sodium reacts with chlorine to form sodium chloride.

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Completed

CHEMISTRY #3123

Explain why ionic compounds have high melting points.

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Completed

CHEMISTRY #3124

Why do ionic compounds conduct electricity when molten but not when solid?

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Completed

CHEMISTRY #3125

Define covalent bonding. Between which types of elements does it occur?

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Completed

CHEMISTRY #3127

Explain why simple covalent substances like iodine have low melting points.

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Completed

CHEMISTRY #3128

Describe metallic bonding using the terms "positive ions" and "sea of delocalized electrons."

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Completed

CHEMISTRY #3130

What is a giant covalent structure? Give two examples.

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Completed

CHEMISTRY #3141

Why are metals good conductors of heat and electricity? Refer to sea of electrons model.

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Completed

CHEMISTRY #3144

Ionic bonding involves the __________ of electrons from a metal to a non-metal.

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Completed

CHEMISTRY #3145

The ions in an ionic compound are arranged in a giant __________.

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Completed

CHEMISTRY #3146

In the solid state, ionic compounds do not conduct electricity because the ions are __________.

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Completed

CHEMISTRY #3147

Covalent bonding involves the __________ of electrons between non-metals.

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CHEMISTRY #3148

A molecule of oxygen (O₂) has a __________ covalent bond.

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Completed

CHEMISTRY #3149

The weak forces between simple covalent molecules are called __________ forces.

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Completed

CHEMISTRY #3150

In metallic bonding, the outer electrons are and form a "".

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Completed

CHEMISTRY #3151

Metals are __________ because they can be hammered into shape without breaking.

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Completed

CHEMISTRY #3152

In diamond, each carbon atom is bonded to __________ other carbon atoms.

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Completed

CHEMISTRY #3153

In graphite, the layers are held together by weak __________ forces.

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Completed

CHEMISTRY #3160

Write the formula for the compound formed between potassium and sulfur.

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Completed

CHEMISTRY #3161

Write the formula for the compound formed between aluminium and oxygen.

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Completed

CHEMISTRY #3174

What is a non-polar covalent bond?

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Completed

CHEMISTRY #3178

A pair of electrons not involved in bonding is called a __________ pair.

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Completed

CHEMISTRY #3180

Different structural forms of the same element are called __________.

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Completed

CHEMISTRY #3184

Give an example of a linear molecule.

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Completed

CHEMISTRY #3185

Give an example of a bent (angular) molecule.

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Completed

CHEMISTRY #3186

Give an example of a tetrahedral molecule.

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Completed

CHEMISTRY #3187

Give an example of a trigonal pyramidal molecule.

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Completed

CHEMISTRY #3199

Classify the bonding in: NaCl, H₂O, Cu, CO₂, diamond.

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Completed

CHEMISTRY #3200

Which type of bond is generally the strongest within a molecule?

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Completed

CHEMISTRY #3210

Complete the sentence: The type of bonding in a substance determines its __________.

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Completed

CHEMISTRY #3027

Element X has atomic number 12 and mass number 24. Calculate protons, neutrons, electrons in neutral atom. Write electron configuration.

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Completed

CHEMISTRY #3028

An atom has 11 protons and 12 neutrons. What is its: a) atomic number, b) mass number, c) number of electrons (if neutral)? Identify the element.

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Completed

CHEMISTRY #3034

Element has two isotopes: lighter 50.0 amu (60% abundance), heavier 52.0 amu (40%). Calculate relative atomic mass.

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Completed

CHEMISTRY #3035

Calculate number of neutrons in: a) ²³₁₁Na, b) ⁴⁰₂₀Ca, c) ⁵⁶₂₆Fe, d) ²³⁵₉₂U.

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Completed

CHEMISTRY #3038

Where are protons, neutrons, and electrons located in an atom?

EASY +15 XP 5 min

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Completed

CHEMISTRY #3039

State the relative mass and charge of: a) proton, b) neutron, c) electron.

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Completed

CHEMISTRY #3040

What does the atomic number (Z) of an element represent?

EASY +15 XP 5 min

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Completed

CHEMISTRY #3041

What does the mass number (A) of an atom represent?

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Completed

CHEMISTRY #3042

What are isotopes?

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Completed

CHEMISTRY #3044

What is the maximum number of electrons in the first three electron shells?

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Completed

CHEMISTRY #3045

What are valence electrons?

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Completed

CHEMISTRY #3046

Why are noble gases chemically unreactive?

EASY +15 XP 5 min

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Completed

CHEMISTRY #3047

Write the electronic configuration of sodium (atomic number 11).

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Completed

CHEMISTRY #3048

Write the electronic configuration of chlorine (atomic number 17).

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Completed

CHEMISTRY #3049

Write the electronic configuration of argon (atomic number 18).

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Completed

CHEMISTRY #3050

Write the electronic configuration of calcium (atomic number 20).

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Completed

CHEMISTRY #3055

How many protons and neutrons does carbon-14 have? Atomic number of carbon is 6.

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Completed

CHEMISTRY #3056

How many protons, neutrons, and electrons in neutral uranium-235? (U atomic number = 92)

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Completed

CHEMISTRY #3057

Helium-4 has atomic number 2 and mass number 4. How many protons, neutrons, and electrons in a neutral atom?

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Completed

CHEMISTRY #3058

Oxygen-18 has atomic number 8. How many neutrons does it have?

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Completed

CHEMISTRY #3059

How many electrons does Na⁺ have? (Na atomic number = 11)

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Completed

CHEMISTRY #3060

How many electrons does Cl⁻ have? (Cl atomic number = 17)

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Completed

CHEMISTRY #3062

Lithium atomic number is 3. How many electrons in Li⁺?

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Completed

CHEMISTRY #3063

Calcium atom has 20 protons. If it forms a Ca²⁺ ion, how many electrons does it have?

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Completed

CHEMISTRY #3067

Define relative molecular mass (Mr).

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Completed

CHEMISTRY #3068

Calculate the relative molecular mass of water (H₂O). (H=1, O=16)

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Completed

CHEMISTRY #3069

Calculate the relative molecular mass of carbon dioxide (CO₂). (C=12, O=16)

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Completed

CHEMISTRY #3070

Calculate the relative molecular mass of sulfuric acid (H₂SO₄). (H=1, S=32, O=16)

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Completed

CHEMISTRY #3073

Write the electronic configuration of potassium (atomic number 19).

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Completed

CHEMISTRY #3076

Which noble gas has the electronic configuration 2,8,8?

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Completed

CHEMISTRY #3077

What is the difference between a cation and an anion?

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Completed

CHEMISTRY #3078

A proton has a __________ charge.

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Completed

CHEMISTRY #3079

An electron has a __________ charge.

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Completed

CHEMISTRY #3080

A neutron has a __________ charge.

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Completed

CHEMISTRY #3081

The atomic number is represented by the symbol __.

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Completed

CHEMISTRY #3082

The mass number is represented by the symbol __.

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Completed

CHEMISTRY #3083

The number of neutrons is represented by the symbol __.

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Completed

CHEMISTRY #3084

Isotopes have the same number of but different numbers of .

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Completed

CHEMISTRY #3085

The outermost electron shell is called the __________ shell.

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Completed

CHEMISTRY #3086

The tendency of atoms to achieve 8 electrons in their outer shell is called the __________ rule.

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Completed

CHEMISTRY #3107

What does the notation ᴬ₂X represent?

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Completed

CHEMISTRY #3108

How many atoms are in one mole of carbon-12?

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Completed

CHEMISTRY #3109

What is the molar mass of a substance?

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Completed

CHEMISTRY #3112

Write the electronic configuration of sulfur (atomic number 16).

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Completed

CHEMISTRY #3114

How are valence electrons related to group number for main group elements?

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Completed

CHEMISTRY #3115

How is the period number related to electron shells?

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Completed

CHEMISTRY #2831

Name the two main gases in dry air and give their approximate percentages by volume.

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Completed

CHEMISTRY #2835

Name three methods of preventing rust, giving an example of each.

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Completed

CHEMISTRY #2836

How is oxygen prepared in the laboratory from hydrogen peroxide? Write the balanced equation.

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Completed

CHEMISTRY #2837

List three physical properties of oxygen.

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Completed

CHEMISTRY #2838

What is the test for oxygen gas?

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Completed

CHEMISTRY #2839

Write word equations for burning of: a) magnesium b) sulfur c) methane in oxygen.

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Completed

CHEMISTRY #2840

Name two common air pollutants and state one source and one harmful effect for each.

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Completed

CHEMISTRY #2841

What is acid rain? Name two gases that cause it.

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Completed

CHEMISTRY #2842

State one use of: a) liquid nitrogen b) oxygen in steel making.

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Completed

CHEMISTRY #2845

A student left a steel knife blade in a damp place for a week. A brown flaky substance appeared. Identify the substance and explain its formation. How could the student have prevented it?

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Completed

CHEMISTRY #2848

Explain why a burning splint is extinguished in a jar of nitrogen, but a glowing splint relights in a jar of oxygen.

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Completed

CHEMISTRY #2854

Air contains about % nitrogen and % oxygen by volume.

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Completed

CHEMISTRY #2855

When copper is heated in air, it forms __________-colored copper(II) oxide.

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Completed

CHEMISTRY #2856

The industrial process for obtaining nitrogen and oxygen from air is called of liquefied air.

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Completed

CHEMISTRY #2857

Rust is chemically known as hydrated __________ oxide.

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Completed

CHEMISTRY #2858

The two conditions for rusting are and .

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Completed

CHEMISTRY #2859

Coating iron with zinc is called __________.

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Completed

CHEMISTRY #2860

In the lab preparation of oxygen, manganese(IV) oxide acts as a __________.

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Completed

CHEMISTRY #2861

The test for oxygen is that it __________ a glowing splint.

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Completed

CHEMISTRY #2862

When sulfur burns in oxygen, it produces gas, which turns moist blue litmus paper .

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CHEMISTRY #2863

A gas that binds strongly to hemoglobin and prevents oxygen transport is __________.

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CHEMISTRY #2864

__________ are a group of chemicals that destroy the ozone layer.

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CHEMISTRY #2865

In an experiment to find the percentage of oxygen in air using copper, initial volume was 100 cm³. After heating, final volume was 79 cm³. Calculate the percentage of oxygen.

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CHEMISTRY #2867

Liquid nitrogen boils at -196°C, liquid oxygen at -183°C. Which gas boils off first as liquid air is warmed?

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CHEMISTRY #2878

Name three greenhouse gases.

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CHEMISTRY #2879

What is the function of the ozone layer?

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CHEMISTRY #2881

Name one source of particulate matter air pollution.

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CHEMISTRY #2883

The trapping of heat in the Earth's atmosphere by certain gases is called the __________ effect.

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CHEMISTRY #2884

Long-term change in global weather patterns is called .

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CHEMISTRY #2885

The total greenhouse gas emissions caused by an individual or activity is called its .

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CHEMISTRY #2886

Energy from sources that are naturally replenished (solar, wind, hydro) is called __________ energy.

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CHEMISTRY #2887

The chemical reaction of a substance with oxygen to produce heat and light is called __________.

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CHEMISTRY #2888

When a fuel burns with insufficient oxygen, producing carbon monoxide, it is called __________ combustion.

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CHEMISTRY #2889

The gain of oxygen or loss of electrons is called __________.

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Completed

CHEMISTRY #2890

The loss of oxygen or gain of electrons is called __________.

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CHEMISTRY #2891

The breakdown of a compound by heating is called __________ decomposition.

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CHEMISTRY #2892

Carbon dioxide turns limewater (calcium hydroxide solution) __________.

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CHEMISTRY #2894

The process by which plants convert CO₂ and water into glucose and oxygen using sunlight is called __________.

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CHEMISTRY #2895

The process by which living organisms release energy from glucose using oxygen is called __________.

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CHEMISTRY #2896

The movement of carbon between the atmosphere, oceans, living things, and rocks is called the __________ cycle.

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CHEMISTRY #2897

Coal, oil, and natural gas are collectively known as __________ fuels.

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CHEMISTRY #2898

Fuels produced from living organisms (e.g., ethanol from corn) are called __________.

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CHEMISTRY #2899

What are the products of complete combustion of a hydrocarbon?

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Completed

CHEMISTRY #2901

List two consequences of global warming.

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CHEMISTRY #2904

A vehicle that produces no exhaust emissions (e.g., hydrogen fuel cell or battery electric) is called a - vehicle.

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CHEMISTRY #2918

In what year was the Paris Agreement on climate change adopted?

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CHEMISTRY #2919

The goal of balancing CO₂ emissions with removal is called -.

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CHEMISTRY #2920

Investing in projects that reduce CO₂ elsewhere to compensate for one's own emissions is called a .

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CHEMISTRY #2741

Name four methods used to separate solid-solid mixtures.

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CHEMISTRY #2742

Explain the difference between decantation and filtration. When would you use each?

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CHEMISTRY #2743

What type of mixture is separated using a separating funnel? Give an example.

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CHEMISTRY #2745

Define chromatography. What are the stationary and mobile phases in paper chromatography?

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CHEMISTRY #2746

State the main ideas of the kinetic theory of matter.

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CHEMISTRY #2747

Describe the arrangement and movement of particles in a liquid.

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CHEMISTRY #2748

How does an impurity affect the melting point of a solid? Give a practical example.

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CHEMISTRY #2749

List three differences between a physical change and a chemical change.

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CHEMISTRY #2750

What is an element? Give the symbols for: sodium, potassium, iron, and gold.

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CHEMISTRY #2751

What is a compound? Give an example and state its chemical formula.

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CHEMISTRY #2752

Write word equations for: a) burning of magnesium in oxygen b) thermal decomposition of limestone (calcium carbonate)

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Completed

CHEMISTRY #2756

Using kinetic theory, explain why a gas can be compressed easily but a solid cannot.

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CHEMISTRY #2757

A student performs paper chromatography on a sample of black ink. After the experiment, they see three spots on the paper. What does this tell you about the ink?

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CHEMISTRY #2758

Is dissolving sugar in water a physical or chemical change? Justify your answer.

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CHEMISTRY #2762

Why is it important to draw the baseline on a chromatography paper in pencil, not in pen?

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CHEMISTRY #2763

To separate iron filings from sand, you would use a __________.

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CHEMISTRY #2764

The liquid that passes through the filter paper during filtration is called the __________.

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CHEMISTRY #2765

A mixture of oil and water can be separated using a __________ funnel.

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CHEMISTRY #2766

In paper chromatography, the Rf value is calculated as (distance moved by substance) divided by (distance moved by __________).

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CHEMISTRY #2767

In a solid, particles __________ about fixed positions.

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CHEMISTRY #2768

An impurity __________ the boiling point of a liquid.

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CHEMISTRY #2769

Rusting of iron is a __________ change.

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CHEMISTRY #2770

A pure substance that cannot be broken down into simpler substances is an __________.

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Completed

CHEMISTRY #2771

The chemical symbol for sodium is , and for gold is .

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CHEMISTRY #2772

The reaction of carbon with oxygen to form carbon dioxide is represented by the word equation: + → __.

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CHEMISTRY #2773

In a chromatography experiment, a blue dye travels 4.5 cm from the baseline. The solvent front travels 6.0 cm. Calculate the Rf value of the blue dye.

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CHEMISTRY #2782

What is crystallization?

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Completed

CHEMISTRY #2783

Name two substances that sublime.

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Completed

CHEMISTRY #2784

Explain diffusion using kinetic theory.

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Completed

CHEMISTRY #2788

What is the difference between a solution and a suspension?

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Completed

CHEMISTRY #2789

Give an example of a colloid.

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CHEMISTRY #2790

What is the Tyndall effect?

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Completed

CHEMISTRY #2791

The scattering of light by colloidal particles is called the __________ effect.

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CHEMISTRY #2793

Why is distilled water used in laboratories and car batteries instead of tap water?

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CHEMISTRY #2794

What is the possible range of Rf values?

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Completed

CHEMISTRY #2798

In chromatography, the solvent that moves through the stationary phase is called the __________ phase.

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CHEMISTRY #2799

The material that stays fixed in place in chromatography is the __________ phase.

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CHEMISTRY #2800

The substance that is dissolved in a solvent to form a solution is called the __________.

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CHEMISTRY #2801

The liquid that dissolves a solute is called the __________.

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CHEMISTRY #2802

A solution that cannot dissolve any more solute at a given temperature is called __________.

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Completed

CHEMISTRY #2803

A solution containing a large amount of solute relative to solvent is __________.

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Completed

CHEMISTRY #2804

A solution containing a small amount of solute relative to solvent is __________.

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Completed

CHEMISTRY #2805

Define solubility.

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Completed

CHEMISTRY #2806

List two factors that affect solubility.

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Completed

CHEMISTRY #2807

How does temperature affect solubility of gases in liquids?

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Completed

CHEMISTRY #2810

How can evaporation be sped up?

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CHEMISTRY #2811

What is the difference between vaporization and evaporation?

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Completed

CHEMISTRY #2816

What does hygroscopic mean?

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CHEMISTRY #2817

Name a common desiccant (drying agent).

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CHEMISTRY #2818

A substance that absorbs moisture from the air is called __________.

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CHEMISTRY #2821

A salt that contains no water of crystallization is called __________.

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CHEMISTRY #2823

What is deposition?

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Completed

CHEMISTRY #2824

What is condensation?

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Completed

CHEMISTRY #2825

What is freezing?

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CHEMISTRY #2829

The pressure exerted by vapor in equilibrium with its liquid is called __________ pressure.

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CHEMISTRY #2830

What is the normal boiling point of a liquid?

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CHEMISTRY #2611

Define chemistry and list four of its main branches.

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Completed

CHEMISTRY #2612

What is matter? Give three general properties of matter.

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Completed

CHEMISTRY #2613

Distinguish between a homogeneous and a heterogeneous mixture, giving an example of each.

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CHEMISTRY #2614

Name two methods used to separate mixtures and explain the principle behind each.

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Completed

CHEMISTRY #2615

What is the difference between a conductor and a non-conductor of electricity? Give two examples of each.

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Completed

CHEMISTRY #2618

List four career paths that require chemistry knowledge.

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CHEMISTRY #2620

What is the function of the air hole on a Bunsen burner? Describe the appearance and use of a luminous flame.

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Completed

CHEMISTRY #2621

State three general safety rules in a chemistry laboratory.

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CHEMISTRY #2622

What first aid would you give to someone who has splashed a chemical into their eyes?

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CHEMISTRY #2627

Why is the non-luminous flame preferred for heating in the lab over the luminous flame?

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CHEMISTRY #2628

Explain why you should never point a test tube towards your friend while heating it.

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CHEMISTRY #2629

A beaker of water is placed on a wire gauze on a tripod and heated with a Bunsen burner. What is the purpose of the wire gauze?

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Completed

CHEMISTRY #2633

Anything that has mass and occupies space is called __________.

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CHEMISTRY #2634

The branch of chemistry that studies carbon compounds is __________ chemistry.

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CHEMISTRY #2635

A mixture where the components are uniformly distributed is called a __________ mixture.

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CHEMISTRY #2636

Materials that allow electricity to pass through them are known as __________.

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Completed

CHEMISTRY #2637

The __________ flame of a Bunsen burner is blue and very hot because of complete combustion.

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CHEMISTRY #2638

The part of the Bunsen burner that controls the amount of air entering is the __________.

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CHEMISTRY #2639

If someone's clothes catch fire, the immediate action is , , and __.

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Completed

CHEMISTRY #2640

A device used to measure precise and variable volumes of liquid during a titration is a __________.

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Completed

CHEMISTRY #2641

Drugs that kill or inhibit bacteria are called __________.

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Completed

CHEMISTRY #2642

The first aid for a chemical splash in the eye is to rinse with plenty of __________ for at least 15 minutes.

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Completed

CHEMISTRY #2643

A block of metal has a mass of 50 g and a volume of 10 cm³. Calculate its density.

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CHEMISTRY #2644

If you have 200 mL of salt solution and you want to obtain the salt by evaporation, what mass of salt would you expect if the solution concentration is 5 g per 100 mL?

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Completed

CHEMISTRY #2645

You need to prepare 500 mL of a copper sulfate solution with a concentration of 2 g per 100 mL. What mass of copper sulfate do you need to dissolve?

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Completed

CHEMISTRY #2651

What is the difference between a physical change and a chemical change? Give an example of each.

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Completed

CHEMISTRY #2652

Distinguish between an element, a compound, and a mixture.

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Completed

CHEMISTRY #2654

List four properties of metals.

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Completed

CHEMISTRY #2655

The smallest particle of an element that retains its chemical properties is called an __________.

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CHEMISTRY #2656

A __________ is formed when two or more atoms chemically bond together.

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CHEMISTRY #2657

The subatomic particle with a positive charge is the __________.

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CHEMISTRY #2658

The subatomic particle with a negative charge is the __________.

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CHEMISTRY #2659

The subatomic particle with no charge (neutral) is the __________.

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CHEMISTRY #2660

What is the atomic number (Z) of an element?

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CHEMISTRY #2661

What is the mass number (A) of an atom?

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CHEMISTRY #2662

What are isotopes?

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CHEMISTRY #2663

How many neutrons are in a carbon-14 atom? (Atomic number of carbon = 6)

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CHEMISTRY #2665

What are valence electrons?

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CHEMISTRY #2666

Why are noble gases (Group 18) unreactive?

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CHEMISTRY #2667

How is a positive ion (cation) formed?

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CHEMISTRY #2668

How is a negative ion (anion) formed?

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CHEMISTRY #2669

What is an ionic bond?

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Completed

CHEMISTRY #2670

What is a covalent bond?

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Completed

CHEMISTRY #2672

What is oxidation in terms of electrons?

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CHEMISTRY #2673

What is reduction in terms of electrons?

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CHEMISTRY #2674

What is a redox reaction?

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CHEMISTRY #2675

What is an acid according to Arrhenius?

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CHEMISTRY #2676

What is a base according to Arrhenius?

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CHEMISTRY #2677

What does the pH scale measure? What pH values are acidic, neutral, and basic?

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CHEMISTRY #2678

What is a neutralization reaction? Write the general equation.

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CHEMISTRY #2679

What colors do blue and red litmus paper turn in acids and bases?

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Completed

CHEMISTRY #2680

Calculate the molecular mass of water (H₂O). (H=1, O=16)

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Completed

CHEMISTRY #2681

Calculate the molecular mass of carbon dioxide (CO₂). (C=12, O=16)

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Completed

CHEMISTRY #2683

How many moles are in 36 grams of water? (H₂O molecular mass = 18 g/mol)

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Completed

CHEMISTRY #2684

Balance the equation: H₂ + O₂ → H₂O

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CHEMISTRY #2685

What type of reaction is: 2Mg + O₂ → 2MgO?

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Completed

CHEMISTRY #2686

What type of reaction is: 2H₂O → 2H₂ + O₂?

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CHEMISTRY #2687

What type of reaction is: CH₄ + 2O₂ → CO₂ + 2H₂O?

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Completed

CHEMISTRY #2688

The SI unit for density is __________.

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Completed

CHEMISTRY #2689

The ability of a substance to dissolve in a solvent is called __________.

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CHEMISTRY #2690

The process of separating solids from liquids using a porous barrier is called __________.

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Completed

CHEMISTRY #2691

The separation technique based on different boiling points is called __________.

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Completed

CHEMISTRY #2692

The technique that separates mixtures based on differential attraction to a stationary and mobile phase is called __________.

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Completed

CHEMISTRY #2695

A solid that forms from a solution during a chemical reaction is called a __________.

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CHEMISTRY #2699

What does the law of conservation of mass state?

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CHEMISTRY #2700

A reaction that releases heat energy is called __________.

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Completed

CHEMISTRY #2701

A reaction that absorbs heat energy is called __________.

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Completed

CHEMISTRY #2702

Rusting of iron is an example of __________.

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Completed

CHEMISTRY #2706

A substance that conducts electricity when dissolved in water or molten is an __________.

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Completed

CHEMISTRY #2707

A substance that does not conduct electricity when dissolved in water is a __________.

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CHEMISTRY #2710

What is an indicator in chemistry?

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CHEMISTRY #2713

What does the "corrosive" safety symbol indicate?

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CHEMISTRY #2714

What does the "flammable" safety symbol indicate?

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CHEMISTRY #2715

What does the "toxic" safety symbol indicate?

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CHEMISTRY #2718

What is a polymer?

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CHEMISTRY #2722

What is the functional group of alcohols?

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CHEMISTRY #2723

What is the functional group of carboxylic acids?

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CHEMISTRY #2724

What functional group characterizes esters?

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CHEMISTRY #2726

The process by which yeast converts sugar into ethanol and carbon dioxide is called __________.

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CHEMISTRY #2728

What is a hydrocarbon?

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CHEMISTRY #2729

What is the general formula for alkanes?

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CHEMISTRY #2730

What is the general formula for alkenes?

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CHEMISTRY #2733

How does burning fossil fuels contribute to global warming?

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CHEMISTRY #2734

What causes acid rain?

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CHEMISTRY #2736

What is hard water?

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CHEMISTRY #2738

Atoms of the same element with different numbers of neutrons are called __________.

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CHEMISTRY #2740

Why is chemistry considered a central science?

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PHYSICS #2526

What is a semiconductor? Give two examples.

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PHYSICS #2528

What is an intrinsic semiconductor?

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PHYSICS #2530

What is doping? Why is it done?

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PHYSICS #2533

What is a p-n junction?

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PHYSICS #2537

What is the knee voltage for a silicon diode? For a germanium diode?

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PHYSICS #2538

What is rectification?

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PHYSICS #2539

Distinguish between half-wave and full-wave rectification.

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PHYSICS #2544

A silicon sample is doped with 10¹⁷ atoms/cm³ of arsenic. Is this n-type or p-type? What are majority and minority carriers?

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PHYSICS #2552

What is the maximum reverse voltage a diode can withstand without breakdown called?

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PHYSICS #2557

A half-wave rectifier supplies a load current of 200 mA. If the input frequency is 50 Hz, calculate the ripple frequency.

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PHYSICS #2565

A full-wave rectifier has an output ripple frequency of 100 Hz. What is the input mains frequency?

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PHYSICS #2577

Intrinsic semiconductors have equal numbers of and .

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PHYSICS #2578

N-type semiconductors are doped with __________ atoms.

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PHYSICS #2579

P-type semiconductors are doped with __________ atoms.

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PHYSICS #2580

In n-type material, __________ are the majority carriers.

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PHYSICS #2581

In p-type material, __________ are the majority carriers.

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PHYSICS #2582

The region near a p-n junction with no free carriers is called the __________.

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PHYSICS #2583

The built-in potential for a silicon diode is approximately __________ V.

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PHYSICS #2584

In forward bias, the depletion layer __________.

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PHYSICS #2585

In reverse bias, the depletion layer __________.

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PHYSICS #2586

The process of converting AC to DC is called __________.

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PHYSICS #2587

A half-wave rectifier uses __________ diode(s).

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PHYSICS #2588

A full-wave bridge rectifier uses __________ diodes.

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Completed

PHYSICS #2589

The ripple frequency for a full-wave rectifier with 50 Hz input is __________ Hz.

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PHYSICS #2590

A __________ capacitor is used to reduce ripple.

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PHYSICS #2593

A __________ diode emits light when forward-biased.

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PHYSICS #2594

A __________ diode generates current when exposed to light.

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PHYSICS #2436

Define radioactivity.

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PHYSICS #2437

Name the three types of nuclear radiation.

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Completed

PHYSICS #2438

What is an alpha particle? Give its composition, charge, and symbol.

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Completed

PHYSICS #2440

What is a gamma ray? How does it differ from alpha and beta particles?

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Completed

PHYSICS #2441

Arrange α, β, and γ in order of increasing penetrating power.

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PHYSICS #2442

Arrange α, β, and γ in order of increasing ionizing ability.

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Completed

PHYSICS #2443

What is half-life?

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Completed

PHYSICS #2447

Name three principles of radiation safety.

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Completed

PHYSICS #2450

Why are gamma rays not deflected by electric or magnetic fields?

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Completed

PHYSICS #2453

A source emits radiation that can be stopped by a sheet of paper. What type is it?

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PHYSICS #2454

A source emits radiation that can penetrate several cm of lead. What type is it?

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PHYSICS #2468

The half-life of iodine-131 is 8 days. If you start with 80 g, how much remains after: a) 8 days b) 16 days c) 24 days d) 32 days

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PHYSICS #2474

A radioactive source has a half-life of 6 hours. What fraction remains after 24 hours?

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PHYSICS #2475

How many half-lives are required for a sample to decay to 6.25% of its original amount?

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PHYSICS #2484

A radiation worker receives a dose of 0.5 mSv at a distance of 1 m from a source. What dose would she receive at 2 m?

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Completed

PHYSICS #2486

What type of shielding would you use for: a) Alpha radiation b) Beta radiation c) Gamma radiation

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Completed

PHYSICS #2487

Why are film badges or TLDs worn by radiation workers?

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Completed

PHYSICS #2498

Radioactivity is the __________ disintegration of unstable nuclei.

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PHYSICS #2499

An alpha particle consists of protons and neutrons.

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Completed

PHYSICS #2500

A beta-minus particle is a fast __________ from the nucleus.

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PHYSICS #2501

Gamma rays are __________ electromagnetic waves.

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PHYSICS #2502

Alpha particles have the ionizing ability and penetrating power.

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Completed

PHYSICS #2503

Gamma rays have the penetrating power and are stopped by thick or __.

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Completed

PHYSICS #2504

The half-life is the time for half the __________ to decay.

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Completed

PHYSICS #2505

In alpha decay, the mass number decreases by and atomic number by .

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Completed

PHYSICS #2506

In beta-minus decay, atomic number by 1, mass number .

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Completed

PHYSICS #2507

Carbon dating uses the isotope with half-life years.

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Completed

PHYSICS #2508

A common medical tracer is __________ with half-life 6 hours.

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Completed

PHYSICS #2509

The three principles of radiation safety are , , and __.

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Completed

PHYSICS #2516

The unit of absorbed dose is the __________ (Gy), equal to 1 joule per kilogram.

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PHYSICS #2517

The unit of equivalent dose (biological effect) is the __________ (Sv).

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PHYSICS #2351

What is the photoelectric effect?

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PHYSICS #2352

Define work function.

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Completed

PHYSICS #2353

Define threshold frequency.

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Completed

PHYSICS #2355

What is a photon?

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Completed

PHYSICS #2358

How does the photocurrent vary with the intensity of incident light?

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Completed

PHYSICS #2360

What is a photocell? Give two uses.

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PHYSICS #2363

Calculate the energy of a photon of red light with wavelength 650 nm. Give your answer in joules and eV.

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PHYSICS #2364

Calculate the energy of a photon of ultraviolet light with wavelength 250 nm.

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Completed

PHYSICS #2375

The work function of a metal is 4.0 eV. What is the maximum wavelength of light that can cause photoemission?

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PHYSICS #2394

The photoelectric effect is the emission of __________ from a metal surface when light shines on it.

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PHYSICS #2395

The minimum energy required to eject an electron from a metal is called the __________.

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PHYSICS #2396

Einstein's photoelectric equation is __________.

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Completed

PHYSICS #2397

The energy of a photon is given by E = = .

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Completed

PHYSICS #2398

Planck's constant has the symbol and value ________ J s.

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PHYSICS #2401

Increasing the intensity of light increases the , not the .

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PHYSICS #2402

The photoelectric effect provides evidence for the __________ nature of light.

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PHYSICS #2403

A device that uses the photoelectric effect to detect light is called a __________.

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PHYSICS #2404

A device that converts light directly into electrical energy using semiconductors is called a __________.

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PHYSICS #2406

Calculate the energy of a 300 nm photon in eV and joules.

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Completed

PHYSICS #2422

de Broglie's equation states λ = __________.

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PHYSICS #2429

A solar cell operates on the __________ effect.

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PHYSICS #2261

Who discovered X-rays and in what year?

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Completed

PHYSICS #2264

What is the function of the filament in an X-ray tube?

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Completed

PHYSICS #2269

Distinguish between hard X-rays and soft X-rays.

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PHYSICS #2273

Why are X-rays classified as ionizing radiation?

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Completed

PHYSICS #2275

Why is lead used for X-ray shielding?

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Completed

PHYSICS #2277

Name three methods of protecting oneself from X-ray exposure.

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PHYSICS #2279

An X-ray tube operates at an accelerating voltage of 60 kV. Calculate the maximum kinetic energy of electrons in eV and joules.

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Completed

PHYSICS #2288

Classify the following X-rays: λ = 0.01 nm, produced at 120 kV

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Completed

PHYSICS #2289

Classify: λ = 0.5 nm, produced at 30 kV

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Completed

PHYSICS #2290

Classify: Energy = 80 keV

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Completed

PHYSICS #2291

Classify: Energy = 5 keV

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Completed

PHYSICS #2307

Why do patients wear lead aprons during dental X-rays?

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Completed

PHYSICS #2318

X-rays were discovered by in .

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PHYSICS #2319

In an X-ray tube, electrons are produced by from a heated .

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Completed

PHYSICS #2320

The target in an X-ray tube is usually made of __________.

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Completed

PHYSICS #2321

The anode is kept at a __________ potential relative to the cathode.

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Completed

PHYSICS #2322

The __________ window allows X-rays to exit the tube.

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PHYSICS #2325

X-rays with high penetrating power are called __________ X-rays.

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Completed

PHYSICS #2326

X-rays with low penetrating power are called __________ X-rays.

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PHYSICS #2328

X-rays are not deflected by or fields.

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Completed

PHYSICS #2329

The ability of X-rays to remove electrons from atoms is called __________.

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Completed

PHYSICS #2331

Lead is used for shielding because it has a high and high .

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Completed

PHYSICS #2332

The __________ principle means keeping radiation doses as low as reasonably achievable.

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Completed

PHYSICS #2333

The thickness of material that reduces X-ray intensity by half is called the __________.

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Completed

PHYSICS #2336

Calculate the power input to an X-ray tube operating at 120 kV and 10 mA.

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Completed

PHYSICS #2337

An X-ray tube has power input 2000 W and X-ray output 15 W. Calculate the efficiency.

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Completed

PHYSICS #2340

Initial intensity 1000 mR, HVL = 3 mm. Find intensity after 9 mm.

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PHYSICS #2101

What is the National Grid?

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PHYSICS #2102

Why is electricity transmitted at high voltage?

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Completed

PHYSICS #2103

What is the formula for power loss in transmission lines?

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Completed

PHYSICS #2104

What is the role of step-up transformers in the National Grid?

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Completed

PHYSICS #2105

What is the role of step-down transformers in the National Grid?

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PHYSICS #2106

What are the colours of live, neutral, and earth wires in a UK plug?

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PHYSICS #2109

What is the purpose of a fuse?

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Completed

PHYSICS #2114

Define the kilowatt-hour (kWh).

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Completed

PHYSICS #2115

How many joules are in 1 kilowatt-hour?

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Completed

PHYSICS #2116

What is the formula for calculating the cost of electricity?

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Completed

PHYSICS #2134

2 kW heater used for 5 hours. Calculate energy in kWh.

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Completed

PHYSICS #2135

100 W bulb left on for 24 hours. Calculate kWh.

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Completed

PHYSICS #2136

3 kW oven used for 2 hours at 30p per kWh. Calculate cost.

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Completed

PHYSICS #2140

Fridge uses 150 kWh in a month. Tariff 30p/kWh. Find cost.

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Completed

PHYSICS #2141

How long must a 500 W appliance run to consume 6 kWh?

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Completed

PHYSICS #2142

Which is more economical: 2 kW for 3 h or 1.5 kW for 4 h?

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Completed

PHYSICS #2153

Power loss in transmission lines is given by P_loss = __________.

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Completed

PHYSICS #2154

Electricity is transmitted at high voltage to reduce __________.

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Completed

PHYSICS #2155

Step-up transformers voltage and current.

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Completed

PHYSICS #2156

Step-down transformers voltage and current.

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Completed

PHYSICS #2157

The live wire colour is __________.

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Completed

PHYSICS #2158

The neutral wire colour is __________.

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Completed

PHYSICS #2159

The earth wire colour is __________.

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Completed

PHYSICS #2160

A ring main circuit connects sockets in a __________.

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Completed

PHYSICS #2161

A fuse protects against excessive __________.

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Completed

PHYSICS #2163

A __________ is a resettable safety device that replaces a fuse.

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Completed

PHYSICS #2165

Double insulated appliances have no __________ wire.

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PHYSICS #2166

1 kWh = __________ J.

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Completed

PHYSICS #2167

Energy (kWh) = (kW) × (hours).

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Completed

PHYSICS #2168

Cost = Energy (kWh) × __________.

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Completed

PHYSICS #2169

Transmission line resistance causes __________ losses.

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Completed

PHYSICS #2172

The National Grid operates at a frequency of __________ Hz in the UK.

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Completed

PHYSICS #2174

An immersion heater is an example of an appliance that uses the __________ effect of current.

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Completed

PHYSICS #2180

The __________ charge on an electricity bill is a fixed daily cost regardless of usage.

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PHYSICS #2181

What are cathode rays?

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Completed

PHYSICS #2188

Which of these is a property of cathode rays?

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Completed

PHYSICS #2192

Name the main parts of a Cathode Ray Oscilloscope.

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Completed

PHYSICS #2193

What is the function of the Y-plates?

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PHYSICS #2194

What is the function of the X-plates?

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Completed

PHYSICS #2198

What is the difference between peak voltage and peak-to-peak voltage?

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Completed

PHYSICS #2203

Electron accelerated through 500 V. Calculate energy in eV and joules.

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Completed

PHYSICS #2216

Y-gain = 1 V/div, spot shifts up 3.4 divisions. What is the DC voltage?

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Completed

PHYSICS #2241

Cathode rays are streams of __________.

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Completed

PHYSICS #2242

The process of releasing electrons from a hot metal surface is called __________.

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Completed

PHYSICS #2243

A cathode ray tube must be evacuated to a high __________.

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Completed

PHYSICS #2244

The __________ controls the brightness of the trace in a CRO.

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PHYSICS #2246

Cathode rays travel in __________ lines.

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PHYSICS #2247

Cathode rays are deflected by and fields.

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Completed

PHYSICS #2248

The screen of a CRO is coated with a __________ material.

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PHYSICS #2249

The __________ plates deflect the beam vertically.

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PHYSICS #2250

The __________ plates deflect the beam horizontally.

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Completed

PHYSICS #2252

The Y-gain control is calibrated in __________ per division.

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Completed

PHYSICS #2253

The time base control is calibrated in __________ per division.

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Completed

PHYSICS #2254

To measure frequency, we first measure the __________ of the waveform.

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Completed

PHYSICS #2257

A CRO can measure both DC and AC __________.

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PHYSICS #2259

The __________ adjusts the sharpness of the trace.

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PHYSICS #2260

The distance from the maximum positive peak to the maximum negative peak is called __________ voltage.

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PHYSICS #2002

What is the SI unit of magnetic flux?

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PHYSICS #2007

List three ways to induce an e.m.f. in a coil.

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PHYSICS #2012

Wire length 0.4 m moves perpendicular to B=0.25 T at 5 m/s. Find e.m.f.

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PHYSICS #2028

A bicycle dynamo produces about 6 V AC when the bicycle is moving at normal speed. If it powers a 6 V, 3 W lamp, find current and resistance.

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Completed

PHYSICS #2031

What is a transformer and what principle does it work on?

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Completed

PHYSICS #2032

Write the transformer equation relating primary and secondary voltages and turns.

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Completed

PHYSICS #2033

What is the difference between a step-up and a step-down transformer?

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Completed

PHYSICS #2038

Primary 500 turns, secondary 50 turns, primary voltage 230 V. Find secondary voltage.

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Completed

PHYSICS #2051

Magnetic flux is given by Φ = __________.

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Completed

PHYSICS #2052

The unit of magnetic flux is the __________.

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PHYSICS #2054

Lenz's Law states that the induced current opposes the __________ that produces it.

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Completed

PHYSICS #2056

An AC generator uses __________ rings to collect current.

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Completed

PHYSICS #2057

A DC generator uses a __________ commutator.

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Completed

PHYSICS #2058

The output of an AC generator is __________ current.

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PHYSICS #2059

The output of a DC generator is __________ current.

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PHYSICS #2060

Mutual induction is the principle of the __________.

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Completed

PHYSICS #2061

For a step-up transformer, Nₛ is __________ than Nₚ.

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Completed

PHYSICS #2062

For a step-down transformer, Nₛ is __________ than Nₚ.

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Completed

PHYSICS #2063

The transformer equation is Vₚ/Vₛ = __________.

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Completed

PHYSICS #2064

In an ideal transformer, VₚIₚ = __________.

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Completed

PHYSICS #2066

The efficiency of a transformer is ( / ) × 100%.

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PHYSICS #2083

A motor converts electrical energy into __________ energy.

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PHYSICS #1901

What are electromagnetic waves?

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PHYSICS #1902

What is the speed of electromagnetic waves in a vacuum?

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PHYSICS #1903

What is the formula relating speed, frequency, and wavelength of EM waves?

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Completed

PHYSICS #1905

What type of wave are electromagnetic waves?

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Completed

PHYSICS #1906

List the seven regions of the electromagnetic spectrum in order of increasing frequency.

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PHYSICS #1907

Which part of the EM spectrum has the longest wavelength?

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Completed

PHYSICS #1908

Which part of the EM spectrum has the highest frequency?

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PHYSICS #1909

Which has a longer wavelength: infrared or ultraviolet?

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Completed

PHYSICS #1910

Which has higher frequency: X-rays or gamma rays?

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Completed

PHYSICS #1911

What is the approximate range of wavelengths for visible light?

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Completed

PHYSICS #1912

Name the colours of visible light in order of increasing wavelength (longest to shortest).

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Completed

PHYSICS #1917

A radio wave has frequency 200 kHz. Calculate wavelength. (c = 3.0 × 10⁸ m/s)

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Completed

PHYSICS #1919

Microwave wavelength 12 cm. Find frequency.

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PHYSICS #1922

Sun distance 1.5 × 10¹¹ m. Time for light to reach Earth?

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PHYSICS #1927

List three uses of radio waves.

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PHYSICS #1935

What are the main natural and artificial sources of infrared radiation?

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PHYSICS #1937

List three uses of infrared in everyday life.

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PHYSICS #1941

What are the primary colours of light?

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PHYSICS #1946

What is the function of the ozone layer?

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PHYSICS #1951

What are the health risks of overexposure to UV radiation?

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PHYSICS #1958

List three medical uses of X-rays.

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PHYSICS #1962

List three uses of gamma rays in medicine and industry.

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PHYSICS #1968

Which part of the EM spectrum has the highest penetrating power?

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PHYSICS #1969

Which part of the EM spectrum is responsible for sunburn?

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PHYSICS #1970

Which part of the EM spectrum is used for TV broadcasting?

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PHYSICS #1971

Which part of the EM spectrum is emitted by all warm objects?

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PHYSICS #1977

All electromagnetic waves travel at the same speed in __________.

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PHYSICS #1978

The speed of light in vacuum is approximately __________ m/s.

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PHYSICS #1979

Electromagnetic waves are __________ waves.

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PHYSICS #1980

The relationship between speed, frequency, and wavelength is __________.

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PHYSICS #1981

Radio waves have the wavelength and frequency.

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PHYSICS #1982

Gamma rays have the wavelength and frequency.

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PHYSICS #1983

The visible spectrum ranges from nm to nm.

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PHYSICS #1984

The colour with the longest wavelength in visible light is __________.

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PHYSICS #1985

The colour with the shortest wavelength in visible light is __________.

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PHYSICS #1986

Microwaves are used in ovens and communication.

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PHYSICS #1987

Infrared radiation is emitted by all __________ objects.

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PHYSICS #1988

Ultraviolet radiation from the Sun is largely absorbed by the __________ layer.

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PHYSICS #1992

__________ is used to kill cancer cells in radiotherapy.

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PHYSICS #1993

__________ cameras detect infrared radiation for night vision.

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PHYSICS #1997

Which EM wave is used for cooking food?

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PHYSICS #1998

Which EM wave is used for viewing inside the human body?

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PHYSICS #1999

Which EM wave is used for detecting forged banknotes?

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Completed

PHYSICS #2000

Which EM wave is used for TV remote controls?

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Completed

PHYSICS #1711

What is the principal axis of a lens?

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Completed

PHYSICS #1712

What is the optical centre of a lens?

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PHYSICS #1713

What is the principal focus of a convex lens?

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PHYSICS #1714

What is the principal focus of a concave lens?

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Completed

PHYSICS #1715

What is the focal length of a lens?

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Completed

PHYSICS #1716

What is the power of a lens?

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Completed

PHYSICS #1717

What is the unit of power of a lens?

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Completed

PHYSICS #1718

What is a converging lens?

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Completed

PHYSICS #1719

What is a diverging lens?

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Completed

PHYSICS #1724

What is the near point of the human eye?

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Completed

PHYSICS #1725

What is the far point of the human eye?

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PHYSICS #1726

What is myopia (short-sightedness)?

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Completed

PHYSICS #1727

How is myopia corrected?

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Completed

PHYSICS #1728

What is hypermetropia (long-sightedness)?

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Completed

PHYSICS #1729

How is hypermetropia corrected?

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Completed

PHYSICS #1749

Lens power +2.5 D. Find focal length and lens type.

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Completed

PHYSICS #1750

Lens power -4 D. Find focal length and type.

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Completed

PHYSICS #1766

A convex lens is also called a __________ lens.

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Completed

PHYSICS #1767

A concave lens is also called a __________ lens.

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Completed

PHYSICS #1768

The point inside a lens through which light passes undeviated is the __________.

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Completed

PHYSICS #1769

The distance from the optical centre to the principal focus is the __________.

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Completed

PHYSICS #1770

The power of a lens is the reciprocal of its __________ in metres.

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Completed

PHYSICS #1771

The unit of power is the __________.

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Completed

PHYSICS #1772

A converging lens has __________ power.

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Completed

PHYSICS #1773

A diverging lens has __________ power.

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Completed

PHYSICS #1778

Myopia is corrected using a __________ lens.

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Completed

PHYSICS #1779

Hypermetropia is corrected using a __________ lens.

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Completed

PHYSICS #1780

The normal near point for a human eye is __________ cm.

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Completed

PHYSICS #1784

In an astronomical telescope, the objective has a focal length and the eyepiece has a focal length.

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Completed

PHYSICS #1791

Focal length must be in __________ when using the power formula P = 1/f.

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Completed

PHYSICS #1792

A concave lens always forms a , , __ image.

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Completed

PHYSICS #1799

A lens of power +1 D has a focal length of __________.

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Completed

PHYSICS #1800

The power of lenses in contact is the __________ of their individual powers.

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Completed

PHYSICS #1631

What is streamline (laminar) flow?

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Completed

PHYSICS #1632

Which of these are characteristics of streamline flow?

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Completed

PHYSICS #1633

What is turbulent flow?

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Completed

PHYSICS #1634

Which of these are characteristics of turbulent flow?

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Completed

PHYSICS #1638

What happens to the velocity of a fluid when it flows from a wide pipe into a narrow pipe?

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Completed

PHYSICS #1639

Why does a river flow faster in narrow sections and slower in wide sections?

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Completed

PHYSICS #1649

Why do racing cars have low, streamlined bodies?

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Completed

PHYSICS #1654

Water flows through pipe area 0.05 m² at 2 m/s. Calculate volume flow rate.

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Completed

PHYSICS #1655

Pipe area at X = 0.1 m², v_X = 1.5 m/s. At Y area = 0.02 m². Find v_Y.

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Completed

PHYSICS #1660

Inlet A₁=0.5 m², v₁=1 m/s. Outlet v₂=4 m/s. Find A₂.

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Completed

PHYSICS #1673

Flow that is smooth and orderly is called __________ flow.

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Completed

PHYSICS #1674

The chaotic, irregular flow with eddies is called __________ flow.

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Completed

PHYSICS #1675

The equation of continuity for an incompressible fluid is __________.

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Completed

PHYSICS #1676

When a fluid flows from a wide pipe to a narrow pipe, its velocity __________.

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PHYSICS #1677

Bernoulli's Principle states that where the speed of a fluid is high, the pressure is __________.

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PHYSICS #1678

The lift on an airplane wing is a result of pressure above the wing and pressure below.

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Completed

PHYSICS #1681

Flow rate is the product of and .

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Completed

PHYSICS #1685

Streamlined shapes reduce __________ and are used in racing cars and aircraft.

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Completed

PHYSICS #1686

The SI unit of volume flow rate is __________.

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Completed

PHYSICS #1687

The continuity equation is based on the principle of conservation of __________.

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Completed

PHYSICS #1701

Laminar flow is also known as __________ flow.

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Completed

PHYSICS #1702

Turbulent flow is characterized by __________ and vortices.

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Completed

PHYSICS #1706

The internal friction in a fluid is called __________.

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PHYSICS #1710

The force that opposes motion through a fluid is called __________.

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Completed

PHYSICS #1561

What is refraction of light?

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Completed

PHYSICS #1563

What is the normal line in the context of refraction?

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PHYSICS #1564

When light passes from air to glass, does it bend towards or away from the normal? Why?

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PHYSICS #1565

What is refractive index?

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Completed

PHYSICS #1566

Write the formula for refractive index using the velocity of light.

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Completed

PHYSICS #1567

What is meant by real depth?

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Completed

PHYSICS #1568

What is meant by apparent depth?

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Completed

PHYSICS #1572

Which of these is an example of total internal reflection?

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Completed

PHYSICS #1573

Why does a pencil placed in a glass of water appear bent or broken at the water's surface?

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Completed

PHYSICS #1609

When light passes from air to glass, it bends __________ the normal.

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PHYSICS #1611

The refractive index of a medium is the ratio of the speed of light in to the speed of light in the .

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Completed

PHYSICS #1612

The apparent depth of an object in water is always __________ than the real depth.

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PHYSICS #1613

Total internal reflection occurs when the angle of incidence is __________ than the critical angle.

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Completed

PHYSICS #1614

The critical angle is related to refractive index by the formula __________.

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PHYSICS #1615

Optical fibres work on the principle of __________.

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Completed

PHYSICS #1620

In total internal reflection, __________ of the incident light is reflected.

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Completed

PHYSICS #1622

In an optical fibre, the core has a __________ refractive index than the cladding.

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Completed

PHYSICS #1481

What does Newton's First Law of Motion state?

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Completed

PHYSICS #1482

Newton's First Law is also known as the Law of __________.

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PHYSICS #1483

What is inertia?

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Completed

PHYSICS #1484

What property of an object determines its inertia?

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Completed

PHYSICS #1485

Why do passengers in a car lurch forward when the car suddenly stops?

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Completed

PHYSICS #1486

Why is it easier to push a shopping cart when it's empty than when it's full?

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Completed

PHYSICS #1488

What does Newton's Second Law of Motion state?

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Completed

PHYSICS #1489

What is the mathematical formula for Newton's Second Law?

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Completed

PHYSICS #1490

In the equation F = ma, what do F, m, and a represent?

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PHYSICS #1491

What is one Newton (1 N) defined as?

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PHYSICS #1492

Calculate the force needed to accelerate a 10 kg mass at 4 m/s².

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PHYSICS #1493

A force of 25 N acts on a 5 kg mass. What is its acceleration?

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Completed

PHYSICS #1494

An object accelerates at 3 m/s² when a force of 12 N is applied. What is its mass?

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Completed

PHYSICS #1495

A 5 kg mass hangs from a spring balance in a stationary lift. What is the reading? (g=10 m/s²)

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Completed

PHYSICS #1501

What does Newton's Third Law of Motion state?

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PHYSICS #1502

Why does a gun recoil when fired?

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Completed

PHYSICS #1508

What is momentum?

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Completed

PHYSICS #1509

What is the formula for momentum?

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Completed

PHYSICS #1510

What is the SI unit of momentum?

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Completed

PHYSICS #1511

Calculate the momentum of a 1500 kg car moving at 20 m/s.

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Completed

PHYSICS #1512

A 0.2 kg ball moving at 15 m/s. Calculate its momentum.

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PHYSICS #1513

What is impulse?

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PHYSICS #1515

A force of 50 N acts on a ball for 0.1 seconds. Calculate the impulse delivered.

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PHYSICS #1526

What is an elastic collision?

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PHYSICS #1527

What is an inelastic collision?

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PHYSICS #1528

What is a perfectly inelastic collision?

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Completed

PHYSICS #1540

Newton's First Law is also known as the Law of __________.

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Completed

PHYSICS #1541

The property of an object to resist changes in its motion is called __________.

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Completed

PHYSICS #1542

The formula for Newton's Second Law is __________.

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Completed

PHYSICS #1543

One Newton is the force that gives a mass of 1 kg an acceleration of __________.

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Completed

PHYSICS #1544

Momentum is defined as __________.

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Completed

PHYSICS #1545

The SI unit of momentum is __________.

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Completed

PHYSICS #1546

Impulse is equal to the change in __________.

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Completed

PHYSICS #1547

In the absence of external forces, the total __________ of a system remains constant.

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Completed

PHYSICS #1548

In an elastic collision, both and are conserved.

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Completed

PHYSICS #1549

Newton's Third Law states that for every action, there is an and reaction.

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Completed

PHYSICS #1550

Rocket propulsion is an example of Newton's __________ Law.

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PHYSICS #1559

Which law explains why a book on a table stays there until pushed?

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Completed

PHYSICS #1401

What is work in physics?

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Completed

PHYSICS #1402

What is the formula for work when force and displacement are in the same direction?

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Completed

PHYSICS #1403

What is the SI unit of work?

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Completed

PHYSICS #1405

Why does a person holding a heavy box stationary do no work in the physics sense?

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Completed

PHYSICS #1406

What is the work done against gravity when lifting an object?

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Completed

PHYSICS #1407

What is energy?

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PHYSICS #1408

What is the SI unit of energy?

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PHYSICS #1409

What is kinetic energy?

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PHYSICS #1410

What is the formula for kinetic energy?

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PHYSICS #1411

What is gravitational potential energy?

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Completed

PHYSICS #1412

What is the formula for gravitational potential energy near Earth's surface?

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PHYSICS #1413

What is the law of conservation of energy?

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PHYSICS #1415

Why does a cyclist go faster going down a hill without pedaling?

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PHYSICS #1416

What is power?

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Completed

PHYSICS #1417

What is the formula for power?

EASY +15 XP 5 min

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Completed

PHYSICS #1418

What is the SI unit of power?

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Completed

PHYSICS #1419

What is one Watt?

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Completed

PHYSICS #1421

What is mechanical advantage (MA)?

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Completed

PHYSICS #1422

What is velocity ratio (VR)?

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Completed

PHYSICS #1423

What is efficiency of a machine?

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Completed

PHYSICS #1425

Why is the efficiency of a real machine always less than 100%?

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Completed

PHYSICS #1431

Calculate work done when 60 N moves an object 12 m in the direction of force.

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PHYSICS #1432

A 15 kg suitcase lifted 1.8 m. Work done? (g=10 m/s²)

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PHYSICS #1433

5 kg object moving at 8 m/s. Calculate KE.

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Completed

PHYSICS #1434

3 kg mass raised 5 m. Calculate GPE. (g=10 m/s²)

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Completed

PHYSICS #1436

Motor does 6000 J of work in 30 seconds. Calculate power.

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Completed

PHYSICS #1444

Same lever, find mechanical advantage.

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Completed

PHYSICS #1446

Block and tackle with 5 ropes supporting load. Find VR.

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Completed

PHYSICS #1447

Same system: load 1000 N, effort 250 N. Find MA.

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Completed

PHYSICS #1449

Incline: length 8 m, height 2 m. Find VR.

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Completed

PHYSICS #1450

Same incline: load 450 N, effort 150 N. Find MA.

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Completed

PHYSICS #1452

Same incline: effort 150 N moved 8 m. Find work input.

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Completed

PHYSICS #1453

Same incline: load 450 N lifted 2 m. Find work output.

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Completed

PHYSICS #1455

Wheel radius 50 cm, axle radius 10 cm. Find VR.

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Completed

PHYSICS #1458

Single movable pulley: load 600 N, effort 320 N. Find MA.

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Completed

PHYSICS #1459

Same pulley, find VR.

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Completed

PHYSICS #1462

Same lever, find MA.

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Completed

PHYSICS #1466

Experiment: load 200 N lifted 2 m. Find work output.

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Completed

PHYSICS #1467

Same experiment: effort 60 N moved 8 m. Find work input.

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Completed

PHYSICS #1468

Same experiment (load 200 N, effort 60 N). Find MA.

EASY +15 XP 5 min

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Completed

PHYSICS #1469

Same experiment (effort distance 8 m, load distance 2 m). Find VR.

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Completed

PHYSICS #1321

What does Ohm's Law state?

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PHYSICS #1322

What is the mathematical formula for Ohm's Law?

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PHYSICS #1323

What is resistance?

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PHYSICS #1324

What are the SI units of resistance?

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Completed

PHYSICS #1327

What is the formula for effective resistance when resistors are connected in series?

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Completed

PHYSICS #1328

What is the formula for effective resistance when resistors are connected in parallel?

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Completed

PHYSICS #1332

What is electrical power?

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Completed

PHYSICS #1337

Why are house lights connected in parallel, not in series?

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Completed

PHYSICS #1342

A 20 Ω resistor has 12 V applied. Calculate the current.

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Completed

PHYSICS #1343

0.5 A flows when 10 V is applied. Find resistance.

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Completed

PHYSICS #1344

240 V, 8 A heater. Find resistance.

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Completed

PHYSICS #1345

5 Ω, 10 Ω, 15 Ω in series. Find total resistance.

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Completed

PHYSICS #1354

Same cell, find lost volts.

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Completed

PHYSICS #1366

3 A through 5 Ω resistor. Calculate power.

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Completed

PHYSICS #1367

230 V, 50 Ω iron. Calculate power.

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Completed

PHYSICS #1368

Heater: 240 V, 2 A, used for 10 minutes. Find power.

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Completed

PHYSICS #1389

Ohm's Law states that V ∝ __________, provided physical conditions remain constant.

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PHYSICS #1390

The SI unit of resistance is the __________.

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PHYSICS #1391

A conductor that obeys Ohm's Law is called an __________ conductor.

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PHYSICS #1392

The V-I graph for a filament lamp is __________, not a straight line.

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PHYSICS #1393

For resistors in series, the effective resistance is the __________ of the individual resistances.

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PHYSICS #1394

For resistors in parallel, the reciprocal of the effective resistance is the __________ of the reciprocals.

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Completed

PHYSICS #1399

One kilowatt-hour is the energy used by a device of power kW used for hour.

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Completed

PHYSICS #1251

What is the law of reflection for waves?

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Completed

PHYSICS #1252

What is refraction?

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Completed

PHYSICS #1254

What is diffraction?

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Completed

PHYSICS #1258

What is interference?

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Completed

PHYSICS #1260

What is constructive interference?

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Completed

PHYSICS #1261

What is destructive interference?

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Completed

PHYSICS #1269

What are nodes in a stationary wave?

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PHYSICS #1270

What are antinodes in a stationary wave?

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PHYSICS #1271

What is the distance between two consecutive nodes in a stationary wave?

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PHYSICS #1272

What is the distance between a node and the next antinode in a stationary wave?

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PHYSICS #1273

What is a progressive (travelling) wave?

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PHYSICS #1276

What is the amplitude of a wave?

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PHYSICS #1284

A water wave has wavelength 2 m and frequency 0.5 Hz. Calculate its speed.

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PHYSICS #1285

A sound wave has frequency 440 Hz and speed 340 m/s. Calculate wavelength.

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PHYSICS #1289

Two waves have a phase difference of π radians. What type of interference?

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PHYSICS #1290

String length 0.8 m, fixed both ends, wave speed 160 m/s. Find fundamental wavelength.

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Completed

PHYSICS #1291

Same string (L=0.8 m, v=160 m/s). Find fundamental frequency.

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Completed

PHYSICS #1301

y = 0.1 sin(50πt - 2πx). Find amplitude.

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Completed

PHYSICS #1305

Same equation, find direction of travel.

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PHYSICS #1191

What is an electric field?

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PHYSICS #1198

What is the formula for electric field strength between parallel plates?

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Completed

PHYSICS #1199

What is the formula for force on a charge in an electric field?

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PHYSICS #1200

What is a capacitor?

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PHYSICS #1201

What is the basic construction of a capacitor?

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PHYSICS #1202

What is capacitance?

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Completed

PHYSICS #1203

What is the formula for capacitance?

EASY +15 XP 5 min

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Completed

PHYSICS #1204

What is the SI unit of capacitance?

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PHYSICS #1208

How does plate area affect capacitance?

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Completed

PHYSICS #1209

How does plate separation affect capacitance?

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PHYSICS #1210

What is a dielectric?

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Completed

PHYSICS #1216

What is the formula for capacitors in parallel?

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Completed

PHYSICS #1217

What is the formula for capacitors in series?

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PHYSICS #1221

What is true about voltage for capacitors in parallel?

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PHYSICS #1222

Two parallel plates 0.02 m apart connected to 200 V. Calculate electric field strength.

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PHYSICS #1223

E field = 5000 N/C, plates 0.04 m apart. Find voltage.

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PHYSICS #1226

Capacitor stores 50 μC at 25 V. Find capacitance.

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PHYSICS #1229

5 μF capacitor with air. Dielectric κ = 4 inserted. New capacitance?

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PHYSICS #1232

Find total C for 2 μF, 3 μF, 5 μF in parallel.

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PHYSICS #1235

6 μF, 6 μF, 3 μF in parallel. Total C?

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PHYSICS #1241

Three equal capacitors C in parallel. Total C?

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PHYSICS #1247

Electric field lines start on charges and end on charges.

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PHYSICS #1248

Between two parallel plates with opposite charges, the electric field is __________.

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PHYSICS #1249

Capacitance is defined as C = __________.

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PHYSICS #1250

The SI unit of capacitance is the __________.

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PHYSICS #1131

What does Joule's Law of Heating state?

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PHYSICS #1132

What is the mathematical formula for Joule heating?

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PHYSICS #1133

Which of these is an application of the heating effect of electric current?

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PHYSICS #1137

What is a fuse?

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PHYSICS #1142

What is earthing?

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PHYSICS #1146

What are the colours and functions of the three wires in a 3-pin plug?

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PHYSICS #1181

If main fuse is 60 A, is the 17.43 A load safe?

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PHYSICS #1182

Joule's Law states that heat produced is proportional to , , and __.

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PHYSICS #1183

The formula for Joule heating is H = __________.

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PHYSICS #1184

A __________ is a safety device that melts when current exceeds a safe value.

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PHYSICS #1186

Earthing connects the metal case of an appliance to the __________ wire.

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PHYSICS #1188

Double-insulated appliances do not require an __________ wire.

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PHYSICS #1189

In a 3-pin plug, the brown wire is connected to the __________ terminal.

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PHYSICS #1067

What is heat capacity?

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PHYSICS #1068

What is the formula for heat capacity?

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PHYSICS #1069

What is the SI unit of heat capacity?

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PHYSICS #1070

What is specific heat capacity?

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PHYSICS #1071

What is the formula for specific heat capacity?

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PHYSICS #1072

What is the SI unit of specific heat capacity?

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PHYSICS #1074

What is the specific heat capacity of water?

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PHYSICS #1076

What is specific latent heat?

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PHYSICS #1077

What is the formula for specific latent heat?

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PHYSICS #1078

What is the SI unit of specific latent heat?

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PHYSICS #1079

What is specific latent heat of fusion?

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PHYSICS #1080

What is specific latent heat of vaporization?

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PHYSICS #1081

What is the approximate specific latent heat of fusion of ice?

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PHYSICS #1082

What is the approximate specific latent heat of vaporization of water?

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PHYSICS #1084

What is the principle behind the method of mixtures?

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PHYSICS #1085

What is a calorimeter?

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PHYSICS #1090

Why does sweating cool the body?

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PHYSICS #1122

Heat capacity is the heat required to raise the temperature of an object by __________.

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PHYSICS #1123

Specific heat capacity is the heat required to raise the temperature of __________ kg of a substance by 1°C.

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PHYSICS #1124

The formula for heat transfer when temperature changes is Q = __________.

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PHYSICS #1125

Specific latent heat is the heat required to change the of 1 kg of a substance without changing .

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PHYSICS #1126

The specific latent heat of fusion of ice is approximately __________ J/kg.

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PHYSICS #1127

The specific latent heat of vaporization of water is approximately __________ J/kg.

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PHYSICS #1128

The method of mixtures is based on the principle that heat = heat .

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PHYSICS #1129

A __________ is used to measure heat transfer in the method of mixtures.

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PHYSICS #1001

What does Boyle's Law state?

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PHYSICS #1002

What is the mathematical formula for Boyle's Law?

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PHYSICS #1003

What does Charles' Law state?

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PHYSICS #1004

What is the mathematical formula for Charles' Law?

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PHYSICS #1005

What does the Pressure Law (Gay-Lussac's Law) state?

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PHYSICS #1006

What is the mathematical formula for the Pressure Law?

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PHYSICS #1008

Convert 0°C to Kelvin.

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PHYSICS #1009

Convert 25°C to Kelvin.

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PHYSICS #1010

Convert -50°C to Kelvin.

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PHYSICS #1011

Convert 100°C to Kelvin.

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PHYSICS #1012

Convert 300 K to Celsius.

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PHYSICS #1013

Convert 373 K to Celsius.

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PHYSICS #1014

Convert 0 K to Celsius.

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PHYSICS #1015

Convert 200 K to Celsius.

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PHYSICS #1020

What is the value of absolute zero in degrees Celsius?

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PHYSICS #1054

Boyle's Law states that P ∝ at constant .

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PHYSICS #1055

Charles' Law states that V ∝ at constant .

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PHYSICS #1056

The Pressure Law states that P ∝ at constant .

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PHYSICS #1057

The formula for Boyle's Law is __________.

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PHYSICS #1058

The formula for Charles' Law is __________.

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PHYSICS #1059

The formula for the Pressure Law is __________.

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PHYSICS #1060

The General Gas Equation is __________.

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PHYSICS #1061

The Ideal Gas Equation is __________.

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PHYSICS #1062

Absolute zero is __________ °C.

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PHYSICS #1063

Absolute zero is __________ K.

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PHYSICS #1064

To convert Celsius to Kelvin, add __________.

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PHYSICS #1065

The universal gas constant R is approximately __________ J/(mol·K).

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PHYSICS #941

What is the difference between distance and displacement?

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PHYSICS #942

What is the difference between speed and velocity?

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PHYSICS #943

What is acceleration?

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PHYSICS #944

What are the SI units of acceleration?

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PHYSICS #946

If a ticker-timer operates at 50 Hz, what is the time interval between dots?

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PHYSICS #947

How can you tell from a ticker tape if an object is moving with constant velocity?

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PHYSICS #948

How can you tell from a ticker tape if an object is accelerating?

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PHYSICS #949

On a displacement-time graph, what does the gradient represent?

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PHYSICS #950

On a velocity-time graph, what does the gradient represent?

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PHYSICS #951

On a velocity-time graph, what does the area under the graph represent?

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PHYSICS #952

Which of these is one of the three equations of linear motion for constant acceleration?

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PHYSICS #953

What is the approximate value of acceleration due to gravity (g) on Earth?

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PHYSICS #954

What is meant by "free fall"?

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PHYSICS #956

A person walks around a block and returns to the starting point. Why is displacement zero but distance non-zero?

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PHYSICS #964

If the gradient of a displacement-time graph is zero, what can you conclude?

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PHYSICS #965

A car travels 100 m East, then 40 m West. Find total distance and displacement.

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PHYSICS #967

A train increases velocity from 10 m/s to 25 m/s in 5 seconds. Calculate acceleration.

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PHYSICS #968

A bicycle decelerates from 15 m/s to 5 m/s in 4 seconds. Calculate deceleration.

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PHYSICS #971

A trolley has 50 dots in 1 second, distance first to last dot = 0.8 m. Find average velocity.

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PHYSICS #972

A car accelerates from rest at 2 m/s² for 8 seconds. Find final velocity.

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PHYSICS #973

For the same car (a=2 m/s², t=8 s, u=0), find distance covered.

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PHYSICS #989

Displacement is a quantity, while distance is a quantity.

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PHYSICS #990

The gradient of a displacement-time graph gives __________.

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PHYSICS #991

The area under a velocity-time graph gives __________.

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PHYSICS #992

The gradient of a velocity-time graph gives __________.

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PHYSICS #993

The three equations of motion apply only when __________ is constant.

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PHYSICS #994

The acceleration due to gravity is approximately __________ m/s².

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PHYSICS #996

If dots on a ticker tape are getting further apart, the object is __________.

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PHYSICS #997

The time between dots on a 50 Hz ticker-timer is __________ seconds.

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PHYSICS #998

Motion under gravity only, with no air resistance, is called __________.

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PHYSICS #999

If acceleration is constant, the velocity-time graph is a __________ line.

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PHYSICS #891

What is a magnetic pole?

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PHYSICS #892

What is the law of magnetic poles?

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PHYSICS #893

Which of these is a magnetic material?

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PHYSICS #894

Which of these is a non-magnetic material?

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PHYSICS #896

What is a magnetic field?

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PHYSICS #898

What is the direction of magnetic field lines outside a bar magnet?

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PHYSICS #923

A magnet is broken into two pieces. What happens?

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PHYSICS #924

Why does a freely suspended magnet not point east-west?

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PHYSICS #933

Like magnetic poles ; unlike poles .

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PHYSICS #934

Magnetic field lines run from pole to pole outside the magnet.

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PHYSICS #937

Steel is a magnetic material; soft iron is a magnetic material.

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PHYSICS #851

What is the typical least count (accuracy) of a standard vernier caliper?

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PHYSICS #852

What is the typical least count (accuracy) of a standard micrometer screw gauge?

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PHYSICS #860

What is standard form (scientific notation)?

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PHYSICS #861

What is the metric prefix for 10⁻⁶?

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PHYSICS #862

What is the metric prefix for 10⁻⁹?

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PHYSICS #863

What is the metric prefix for 10³?

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PHYSICS #864

What is the metric prefix for 10⁶?

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PHYSICS #875

How many significant figures are in the number 1234?

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PHYSICS #879

How many significant figures are in 5600 (without context)?

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PHYSICS #882

Convert 5 mm to metres.

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PHYSICS #883

Convert 2.3 km to metres.

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PHYSICS #888

A distance is 1500 m. Write in kilometres and standard form.

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PHYSICS #811

What is the centre of gravity of an object?

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PHYSICS #812

Where is the centre of gravity of a uniform metre rule?

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PHYSICS #813

Where is the centre of gravity of a uniform circular disc?

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PHYSICS #816

What is meant by equilibrium?

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PHYSICS #817

What is stable equilibrium?

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PHYSICS #818

Which of these is an example of stable equilibrium?

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PHYSICS #819

What is unstable equilibrium?

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PHYSICS #820

Which of these is an example of unstable equilibrium?

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PHYSICS #821

What is neutral equilibrium?

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PHYSICS #822

Which of these is an example of neutral equilibrium?

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PHYSICS #823

What two main factors affect the stability of an object?

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PHYSICS #827

Why are tall, narrow furniture items often fixed to the wall?

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PHYSICS #828

A tall glass is more likely to tip over than a short, wide one. Why?

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PHYSICS #832

What precautions do double-decker bus drivers take when cornering?

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PHYSICS #843

The point through which the entire weight of an object acts is called the __________.

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PHYSICS #844

For a uniform rod, the centre of gravity is at its __________.

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PHYSICS #846

An object that returns to its original position after a slight displacement is in __________ equilibrium.

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PHYSICS #847

An object that moves further away after a slight displacement is in __________ equilibrium.

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PHYSICS #848

A ball on a flat table is in __________ equilibrium.

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PHYSICS #849

Stability increases with a base and a centre of gravity.

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PHYSICS #759

What is the difference between a concave and a convex mirror?

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PHYSICS #760

Which of these is a common use of a concave mirror?

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PHYSICS #761

Which of these is a common use of a convex mirror?

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PHYSICS #767

What is the relationship between focal length (f) and radius of curvature (R) for a spherical mirror?

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PHYSICS #768

Why is a concave mirror called a converging mirror?

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PHYSICS #769

Why is a convex mirror called a diverging mirror?

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PHYSICS #773

For a concave mirror, when the object is at C, the image is:

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PHYSICS #777

What type of image is always formed by a convex mirror?

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PHYSICS #804

For a spherical mirror, f = __________.

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PHYSICS #805

The centre of the mirror surface is called the __________.

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PHYSICS #806

The point where parallel rays converge (or appear to diverge) is the __________.

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PHYSICS #807

A concave mirror is also called a __________ mirror.

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PHYSICS #714

What is a solenoid?

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PHYSICS #715

What type of magnet does a solenoid resemble when current flows?

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PHYSICS #737

What is an advantage of using an electromagnet instead of a permanent magnet?

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PHYSICS #740

A conductor of length 0.5 m carries 3 A perpendicular to a magnetic field of 0.2 T. Calculate the force.

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PHYSICS #749

Oersted discovered that a current-carrying wire produces a __________ field.

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PHYSICS #751

A solenoid produces a field similar to that of a __________ magnet.

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PHYSICS #758

The force on a current-carrying conductor in a magnetic field is called the __________ effect.

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PHYSICS #611

What is the main difference between a wave pulse and a continuous wave?

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PHYSICS #612

What is a transverse wave?

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PHYSICS #613

Which of these are transverse waves?

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PHYSICS #614

What is a longitudinal wave?

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PHYSICS #615

Which of these are longitudinal waves?

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PHYSICS #616

What are the parts of a transverse wave called?

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PHYSICS #617

What are the parts of a longitudinal wave called?

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PHYSICS #618

What is the amplitude of a wave?

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PHYSICS #620

What is the wavelength of a wave?

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PHYSICS #621

What is the frequency of a wave?

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PHYSICS #622

What are the units of frequency?

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PHYSICS #623

What is the period of a wave?

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PHYSICS #624

How are period and frequency related?

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PHYSICS #625

What is the wave equation?

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PHYSICS #627

If you increase the frequency of a wave, what happens to its wavelength if speed is constant?

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PHYSICS #629

A student shakes a rope faster (higher frequency). What happens to wavelength?

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PHYSICS #631

How does particle motion differ between transverse and longitudinal waves?

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PHYSICS #632

If a wave has a high frequency, what can you say about its period?

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PHYSICS #634

On a transverse wave diagram, where do you measure amplitude?

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PHYSICS #635

On a longitudinal wave diagram, wavelength is the distance between __________.

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PHYSICS #636

A wave has frequency 50 Hz and wavelength 2 m. Calculate its speed.

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PHYSICS #637

A wave travels at 10 m/s and has wavelength 0.5 m. Calculate frequency.

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PHYSICS #638

A sound wave has frequency 440 Hz and speed 340 m/s. Calculate wavelength.

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PHYSICS #639

A water wave has speed 1.5 m/s and frequency 0.75 Hz. Find wavelength.

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PHYSICS #640

A wave has period 0.02 seconds. Calculate its frequency.

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PHYSICS #641

A wave has frequency 200 Hz. Calculate its period.

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PHYSICS #645

10 waves in 5 seconds, wavelength 0.3 m. Find frequency.

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PHYSICS #646

For same slinky (10 waves in 5 s), find period.

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PHYSICS #647

For same slinky (f=2 Hz, λ=0.3 m), find speed.

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PHYSICS #648

A wave has speed 20 m/s and frequency 10 Hz. What is the distance between successive crests?

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PHYSICS #521

What is the moment of a force?

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PHYSICS #522

What is the formula for the moment of a force?

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PHYSICS #523

What is the SI unit of moment?

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PHYSICS #524

What is a clockwise moment?

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PHYSICS #525

What is an anticlockwise moment?

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PHYSICS #531

How does the distance from the pivot affect the moment for a given force?

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PHYSICS #532

Why is it easier to loosen a nut with a long spanner than a short one?

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PHYSICS #533

A force of 25 N is applied at a perpendicular distance of 0.5 m from a pivot. Calculate the moment.

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PHYSICS #534

A force of 40 N produces a moment of 12 N m. Calculate the perpendicular distance from the pivot.

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PHYSICS #547

Why is a door handle placed as far from the hinges as possible?

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PHYSICS #551

The turning effect of a force is called its __________.

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PHYSICS #552

Moment = force × __________ distance from pivot.

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PHYSICS #553

The SI unit of moment is the __________.

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PHYSICS #554

The principle of moments states that for equilibrium, clockwise moments = __________ moments.

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PHYSICS #556

The centre of gravity of a uniform rod is at its __________.

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PHYSICS #557

Why is it easier to open a door by pushing at the edge rather than near the hinges?

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PHYSICS #558

A 400 N child sits 1.5 m from a seesaw pivot. How far from pivot must a 600 N child sit to balance?

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PHYSICS #559

A wrench extender (a pipe over the handle) increases the moment. What does this allow?

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PHYSICS #411

What is electrostatics?

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PHYSICS #412

What are the three subatomic particles and their charges?

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PHYSICS #413

What makes an atom electrically neutral?

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PHYSICS #414

How does an object become positively charged?

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PHYSICS #415

How does an object become negatively charged?

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PHYSICS #416

What is the law of charges?

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PHYSICS #431

Why does lightning tend to strike tall buildings and trees?

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PHYSICS #436

Why do you get a small electric shock after walking on a nylon carpet and touching a metal doorknob?

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PHYSICS #439

After the spheres (both positive) are separated, will they attract or repel?

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PHYSICS #442

Why is it dangerous to stand under an isolated tree during a thunderstorm?

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PHYSICS #446

The study of stationary electric charges is called __________.

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PHYSICS #447

The nucleus contains and .

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PHYSICS #448

A neutral atom has equal numbers of and .

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PHYSICS #449

An object becomes positively charged when it __________ electrons.

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PHYSICS #450

Like charges ; unlike charges .

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PHYSICS #451

When a polythene rod is rubbed with wool, the rod becomes __________ charged.

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PHYSICS #455

A lightning conductor has a __________ point to encourage corona discharge.

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PHYSICS #291

What is conduction?

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PHYSICS #292

What is convection?

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PHYSICS #293

What is thermal radiation?

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PHYSICS #296

Why is wool a good insulator?

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PHYSICS #301

How does surface colour affect absorption and emission of radiation?

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PHYSICS #304

Why are cooking pots made of metal but have plastic/wooden handles?

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PHYSICS #305

Why does a metal spoon in hot tea become warm while a wooden spoon does not?

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PHYSICS #306

Why are overhead power lines left slightly slack in summer?

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PHYSICS #308

Why wear light-coloured clothes in summer and dark-coloured in winter?

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PHYSICS #331

Heat transfer in solids is mainly by __________.

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PHYSICS #333

Materials that do not conduct heat well are called __________.

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PHYSICS #334

The transfer of heat by the movement of a fluid is called __________.

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PHYSICS #335

A __________ black surface is the best absorber and emitter of radiation.

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PHYSICS #336

A __________ surface is the best reflector of radiation.

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PHYSICS #340

In a solar heater, the collector is painted black to __________ radiation.

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PHYSICS #343

Which of these reduces heat loss from a house by conduction?

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PHYSICS #349

Why do dark-coloured cars get hotter inside on sunny days than light-coloured cars?

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PHYSICS #241

What is heat transfer?

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PHYSICS #242

What are the three methods of heat transfer?

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PHYSICS #243

What is conduction?

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PHYSICS #244

What is convection?

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PHYSICS #245

What is thermal radiation?

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PHYSICS #246

What is the difference between a conductor and an insulator?

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PHYSICS #247

Which of these is a good conductor of heat?

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PHYSICS #248

Which of these is a good insulator?

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PHYSICS #250

Does radiation require a medium (matter) to transfer heat?

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PHYSICS #255

Why do saucepans often have plastic or wooden handles?

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PHYSICS #256

Why are oven gloves made of thick fabric?

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PHYSICS #265

Why are roofs painted white in hot countries?

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PHYSICS #270

In the ball and ring experiment, a metal ball passes through a ring at room temperature but not when heated. What does this demonstrate?

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PHYSICS #280

Which of these is NOT a method of reducing heat loss from a house?

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PHYSICS #282

Which of these is an example of heat transfer by conduction?

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PHYSICS #283

Which of these is an example of heat transfer by convection?

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PHYSICS #284

Which of these is an example of heat transfer by radiation?

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PHYSICS #285

The transfer of heat through a solid without movement of the material itself is called __________.

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PHYSICS #286

The transfer of heat through a fluid by the movement of the fluid itself is called __________.

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PHYSICS #287

The transfer of heat through electromagnetic waves (infrared) is called __________.

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PHYSICS #182

What is linear expansion?

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PHYSICS #184

What is a bimetallic strip?

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PHYSICS #187

Which of these is a practical application of a bimetallic strip?

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PHYSICS #188

Why are gaps left between railway tracks?

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PHYSICS #190

Why do telephone wires sag more in summer than in winter?

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PHYSICS #192

What is the structure of a liquid-in-glass thermometer?

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PHYSICS #195

Why does ice float on water?

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PHYSICS #199

How can you demonstrate that gases expand when heated?

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PHYSICS #202

Why are concrete roads built with expansion joints filled with tar?

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PHYSICS #212

Why does a balloon partially inflate when placed in warm water?

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PHYSICS #216

Convert 0°C to kelvin.

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PHYSICS #217

Convert 27°C to kelvin.

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PHYSICS #218

Convert -23°C to kelvin.

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PHYSICS #228

The increase in length of a solid on heating is called __________ expansion.

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PHYSICS #229

A device made of two different metals joined together is a __________ strip.

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PHYSICS #230

Gaps left in railway tracks allow for __________ in summer.

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PHYSICS #232

Water has its maximum density at __________ °C.

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PHYSICS #233

Ice floats on water because its density is __________ than that of water.

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PHYSICS #237

When a gas is heated at constant pressure, its volume __________.

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PHYSICS #136

Which of these is evidence that matter is made of tiny particles?

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PHYSICS #140

What is diffusion?

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PHYSICS #141

Which of these is an example of diffusion in gases?

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PHYSICS #142

Which of these is an example of diffusion in liquids?

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PHYSICS #145

How are particles arranged in a solid?

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PHYSICS #146

How are particles arranged in a liquid?

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PHYSICS #147

How are particles arranged in a gas?

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PHYSICS #148

Why does a solid have a fixed shape?

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PHYSICS #150

Why is a gas easier to compress than a liquid?

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PHYSICS #151

What is cohesion?

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PHYSICS #152

What is adhesion?

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PHYSICS #158

What is capillarity (capillary action)?

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PHYSICS #159

Which of these is an example of capillarity?

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PHYSICS #162

Sugar added to tea sweetens the whole cup without stirring. What explains this?

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PHYSICS #163

A drop of food colouring is placed on still water. Over time it spreads. Why?

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PHYSICS #164

Why does the smell of cooking spread across a room?

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PHYSICS #165

Why does a puddle of water dry faster on a warm day than on a cool day?

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PHYSICS #166

In which beaker does ink spread faster: hot water or cold water?

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PHYSICS #170

How does a paper towel soak up a water spill?

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PHYSICS #179

Who first observed Brownian motion?

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PHYSICS #180

A crystal of copper(II) sulfate is placed at the bottom of a beaker of water. What happens over a week?

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PHYSICS #127

At a point in a fluid at rest, pressure acts ________.

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PHYSICS #129

If area doubles while force stays the same, pressure ________.

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PHYSICS #130

A blood pressure reading of 120/80 means ________.

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PHYSICS #076

What is the correct definition of pressure?

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PHYSICS #077

What is the SI unit of pressure?

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PHYSICS #079

What two factors affect pressure in solids?

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PHYSICS #080

Which of these uses a large area to reduce pressure?

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PHYSICS #081

Why do camels have wide feet?

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PHYSICS #086

Which device uses Pascal's principle to multiply force?

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PHYSICS #089

What is a barometer used for?

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PHYSICS #095

A force of 50 N is applied on an area of 2 m². Calculate the pressure.

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PHYSICS #096

A block of weight 600 N rests on a surface with dimensions 1.2 m by 0.8 m. Find the pressure exerted.

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PHYSICS #099

For the block above (mass 75 kg), calculate its weight (g = 10 N/kg).

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PHYSICS #110

Why does a tractor with wide tyres not sink into soft mud as easily as a car?

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PHYSICS #112

Why do some tables have wide flat feet?

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PHYSICS #113

Why is a dam built thicker at the bottom than at the top?

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PHYSICS #074

Which instrument gives the most precise measurement of length?

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PHYSICS #031

Which of the following is a base quantity in SI units?

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PHYSICS #032

Which of the following is a derived quantity?

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PHYSICS #033

What is the SI unit of length?

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PHYSICS #034

What is the SI unit of mass?

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PHYSICS #035

What is the SI unit of time?

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PHYSICS #036

What is the SI unit of area?

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PHYSICS #037

What is the SI unit of volume?

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PHYSICS #038

What is the SI unit of density?

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PHYSICS #039

What is the correct formula for density?

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PHYSICS #047

A rock sinks in water. What can you conclude about its density?

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PHYSICS #048

What is the main use of a measuring cylinder?

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PHYSICS #049

Why is the displacement method used?

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PHYSICS #053

Which instrument is used to measure mass?

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PHYSICS #054

Which instrument is used to measure weight?

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PHYSICS #058

How do you calculate the volume of a rectangular block?

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PHYSICS #059

A cube has side length 3 cm. What is its volume?

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PHYSICS #062

Where would your weight be the greatest?

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PHYSICS #064

What is the formula relating weight (W), mass (m), and gravitational field strength (g)?

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PHYSICS #066

A simple pendulum completes 20 oscillations in 40 seconds. What is its period?

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PHYSICS #068

What precaution should be taken when using a metre rule?

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PHYSICS #070

Convert 250 g to kg.

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PHYSICS #001

Which of the following is a valid effect of a force on an object?

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PHYSICS #002

Which of the following is an example of a non-contact force?

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PHYSICS #004

What is the resultant force when a 10 N force east and a 4 N force west act on the same object?

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PHYSICS #006

Which of the following is an advantage of friction?

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PHYSICS #010

A bag of sugar has a mass of 5 kg. Calculate its weight on Earth where g = 10 N/kg.

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PHYSICS #012

A rock has a mass of 12 kg. On a different planet, its weight is 48 N. What is the value of 'g' on that planet?

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PHYSICS #013

Two forces act on a box: 15 N to the right and 7 N to the left. Calculate the resultant force.

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PHYSICS #022

Why is it more difficult to walk on a very slippery, icy surface than on a dry concrete road?

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PHYSICS #025

Why do machinery parts need to be oiled regularly?

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PHYSICS #026

Which has less friction: sliding or rolling?

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Think. Question. Solve. EdVibe Science Platform

Describe how chlorine gas is prepared in the laboratory using manganese(IV) oxide. Write the equation.

Explain the bleaching action of chlorine. How does it differ from that of sulphur dioxide?

Describe the "fountain experiment" and what it demonstrates.

Explain why chlorine water loses its color and bleaching power when exposed to sunlight.

A student prepares chlorine using KMnO₄ and HCl. Why is this reaction faster than using MnO₂?

Why is sodium hypochlorite manufactured using cold, dilute NaOH, not hot concentrated NaOH?

Explain why dry hydrogen chloride gas does not turn blue litmus red, but hydrochloric acid does.

Why is hydrochloric acid considered a strong acid but not an oxidizing agent (dilute), while concentrated H₂SO₄ is both?

Why is it dangerous to mix household bleach (containing NaOCl) with acidic toilet cleaners? What gas could be produced?

Explain how chlorine is used to purify drinking water. What are the advantages and potential concerns?

Bleaching powder is made by reacting chlorine with __________.

Write balanced equation for preparation of chlorine from KMnO₄ and HCl.

Write equation for reaction of chlorine with hot concentrated NaOH.

What volume of chlorine gas at RTP (24 dm³/mol) from 43.5 g MnO₂?

Compare and contrast properties and reactions of chlorine and hydrogen chloride. How would you distinguish them with chemical tests?

Design a flow chart for industrial production of sodium hypochlorite from common salt, including electrolysis and subsequent reaction.

Explain why chlorine is a powerful oxidizing agent, using its electron configuration and position in periodic table.

Describe chemical tests (using chlorine water and organic solvent) to identify NaCl, NaBr, and NaI.

How is reaction between Cl₂ and NaOH used to make both bleach and chlorates? What conditions determine product?

Why is it important to store bleach in opaque (dark) containers? Write the decomposition equation.

Explain why chlorine can displace bromine from KBr, but iodine cannot displace chlorine from KCl.

Using standard reduction potentials, explain why Cl₂ displaces Br⁻ but Br₂ cannot displace Cl⁻.

Name two other oxidizing agents that can be used to generate chlorine gas from HCl.

Excess chlorine reacts with ammonia to form __________ which is explosive.

Chloramine (NH₂Cl) is used as a disinfectant instead of chlorine because it produces fewer __________ by-products.

What are the three main products of brine electrolysis and how are they separated?

In the __________ cell for brine electrolysis, a cation-exchange membrane separates the anode and cathode compartments.

Why are mercury cells for chlorine production being phased out?

Chlorination of water containing organic matter can produce __________ which are potentially carcinogenic.

What is the approximate formula of bleaching powder?

Write the equation for reaction of bleaching powder with dilute acid.

In the mercury cell, sodium forms an __________ with mercury at the cathode.

Compare chlorine, hydrogen peroxide, and sulfur dioxide as bleaching agents.

What are the oxidation states of chlorine in Cl₂, HOCl, ClO₂⁻, ClO₃⁻, ClO₄⁻?

__________ dioxide (ClO₂) is used as a more environmentally friendly bleaching agent for paper pulp.

Write the equation for reaction of chlorine with sodium thiosulfate (used to dechlorinate water).

Describe the Frasch process for extracting sulphur. Why is this method used?

State two chemical properties of SO₂, with equations.

List the optimum conditions for the Contact Process and explain why they are chosen.

Why is SO₃ not absorbed directly into water to make sulphuric acid?

Explain why rhombic sulphur is stable at room temperature, while monoclinic sulphur is stable above 96°C.

Why is sulphur dioxide collected by upward displacement of air, not over water?

Explain the bleaching action of sulphur dioxide. How does it differ from chlorine bleaching?

Why is 450°C used instead of a lower temperature that would give higher equilibrium yield of SO₃?

Write equations for concentrated H₂SO₄ with: a) Copper, b) Sugar, c) NaCl, d) KNO₃.

How does sulphur dioxide contribute to acid rain? Write the equations involved.

SO₃ is absorbed in __________ to form oleum.

Write equation for reaction of SO₂ with hydrogen sulfide.

Write equation for formation of oleum.

Write equation for dilution of oleum to form sulphuric acid.

Write equation for reaction of concentrated H₂SO₄ with carbon.

Calculate mass of sulphur needed to produce 100 kg of H₂SO₄ (98% yield assumed? Actually 100% yield). S=32, H₂SO₄=98.

What volume of SO₂ at RTP (24 dm³/mol) from 6.3 g Na₂SO₃ (M=126) with excess HCl?

If 100 g SO₂ is converted to SO₃ with 98% yield, mass of SO₃ produced? SO₂=64, SO₃=80

Calculate mass of H₂SO₄ produced from 100 g oleum (H₂S₂O₇). H₂S₂O₇=178, H₂SO₄=98.

Compare and contrast allotropes of carbon (diamond, graphite) with allotropes of sulphur.

Design a flow chart for industrial production of H₂SO₄ from elemental sulphur.

Explain why H₂SO₄ is both an acid and an oxidizing agent. Give examples of each.

Describe chemical tests to identify Na₂SO₃, Na₂SO₄, and Na₂CO₃.

How does combustion of S-containing fossil fuels lead to acid rain, and how can it be mitigated?

Why is V₂O₅ used as catalyst in Contact Process? What happens if catalyst is poisoned?

Using equilibrium and kinetics, explain why Contact Process conditions are a compromise.

Write the equation for SO₂ reducing acidified K₂Cr₂O₇.

What is the chemical formula of oleum?

The biological process where sulphur compounds are oxidized or reduced by microbes is called the __________ cycle.

The reaction of SO₃ with HCl produces __________ __________.

When molten sulphur is poured into cold water, it forms a rubbery form called __________ sulphur.

What happens to the colour of molten sulphur as it is heated from 120°C to 180°C?

Why does the viscosity of molten sulphur decrease at very high temperatures (>200°C)?

Define: a) Standard enthalpy of formation (ΔH°f) b) Standard enthalpy of combustion (ΔH°c) c) Standard enthalpy of solution (ΔH°sol)

Write the equation relating enthalpy of solution, lattice energy, and hydration energy.

Explain why magnesium oxide has a much more negative lattice energy than sodium chloride.

Why do we use Hess's Law to calculate enthalpy changes that cannot be measured directly?

Ammonium nitrate dissolves in water and the solution becomes cold. Explain in terms of lattice energy and hydration energy.

Sodium hydroxide dissolves in water and the solution becomes hot. Explain in terms of lattice energy and hydration energy.

Explain why lattice energy of MgO is much larger than NaCl. Refer to ionic charges and radii.

Why does KCl have a less exothermic lattice energy than NaCl?

Explain why hydration energy of Al³⁺ is much more negative than that of Na⁺.

Student measures temperature decrease when NH₄Cl dissolves. Infer relative magnitudes of lattice and hydration energy.

The reaction of SO₃ with HCl produces .

The ability of a gas to trap heat compared to CO₂ is called its potential.