In a Vernier calipers, when both jaws touch each other, zero of the Vernier scale is shifted to the right of zero of the main scale and $7^{\text{th}}$ Vernier division coincides with a main scale reading. If the value of $1$ main scale division is $1$ mm and there are $10$ Vernier scale divisions, then the Vernier caliper has
Answer: (C) $0.07$ cm positive zero error
Concept. With the jaws closed, a vernier zero to the right of the main-scale zero means the instrument already reads more than zero: a positive zero error of (coinciding division) $\times$ LC.
Step 1. Least count. $1\,\text{MSD}=1$ mm, $10$ VSD: $\text{LC}=\dfrac{1}{10}=0.1$ mm $=0.01$ cm.
Step 2. Zero error. The $7$th vernier line coincides:
$$e=+7\times0.01\ \text{cm}=+0.07\ \text{cm}$$
Answer. $0.07$ cm positive zero error (Option C).
Solution by Sreeraj P, M.Sc Physics
