12.0 MEASUREMENT II

Measurement II builds upon the basic concepts of measurement by introducing more precise instruments and the mathematical rigor required in scientific work. This chapter covers the correct use of vernier calipers and micrometer screw gauges, how to identify and correct zero errors, and the importance of significant figures and SI prefixes. Mastery of these topics is essential for accurate experimental work in physics and engineering.

12.1 PRECISE INSTRUMENTS

In Form 1, you learned about metre rules and measuring cylinders. For more precise measurements, we use vernier calipers and micrometer screw gauges. These instruments can measure lengths to a fraction of a millimetre.

12.1.1 Vernier Calipers

Vernier calipers are used to measure lengths, depths, and internal/external diameters with an accuracy of typically 0.1 mm (0.01 cm) or better.

Construction:

• Main scale (fixed): Graduated in centimetres and millimetres (like a ruler).
• Vernier scale (sliding): A short, movable scale that slides along the main scale. It has a specific number of divisions (usually 10) that cover a length slightly less than the same number of main scale divisions.
• Jaws: Upper jaws (for internal measurements) and lower jaws (for external measurements).
• Depth probe: A thin rod attached to the sliding part for measuring depths.

How to read Vernier Calipers:

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