Measurements II

Syllabus tag: KCSE | Physics | Form 2 | Topic 12 Measurements II

Lesson objectives

By the end of this topic, you should be able to:

• Read and use vernier callipers correctly.
• Read and use a micrometer screw gauge correctly.
• Account for zero error in both instruments.
• Estimate the diameter of a molecule by the oil drop experiment.

Summary

Vernier callipers measure to 0.01 cm and a micrometer screw gauge to 0.01 mm, far more precisely than a metre rule. Both readings are the main scale plus the vernier or thimble reading, and both must be corrected for zero error. The oil drop experiment estimates molecular size at about 10⁻⁹ m.