CHAPTER 8: HEATING EFFECT OF AN ELECTRIC CURRENT

When electric current flows through a conductor, it encounters resistance. Overcoming this resistance requires energy, which is released as heat. This heating effect is both useful (in heaters, kettles, irons, and lamps) and dangerous (overheating wires can cause fires). Understanding this effect and the safety devices that protect us is essential knowledge for everyone.

8.1 JOULE'S LAW OF HEATING

James Prescott Joule studied the relationship between electric current and heat production. His findings form the basis of our understanding of electrical heating.

8.1.1 Statement of Joule's Law

The heat produced in a conductor when an electric current flows through it is directly proportional to:

• The square of the current (I²)
• The resistance of the conductor (R)
• The time for which the current flows (t)

8.1.2 Mathematical Formulation

H = I² × R × t

Where:

• H = heat energy produced (in Joules, J)
• I = current flowing through the conductor (in Amperes, A)
• R = resistance of the conductor (in Ohms, Ω)
• t = time for which current flows (in seconds, s)

Using Ohm's Law (V = IR), we can derive two other useful forms:

H = V × I × t

H = (V² / R) × t

Where V i