Question

In a vernier calipers, the zero of the vernier scale is to the left of the zero of the main scale when the movable jaw is in contact with the fixed jaw. If the seventh division on the vernier scale coincides with the 5th division on the main scale, determine the zero error. Take 1 MSD = 1 mm, and 20 VSD = 19 MSD.

• A. -6.5 mm
• B. 16.5 mm
• C. -0.65 mm
• D. 1.65 mm

Answer 1

The correct option is C -0.65 mm

$\begin{array}{cc}1MSD& =1mm\\ 20VSD& =19MSD\\ 1VSD& =\frac{19}{20}MSD\\ 1VSD& =0.95MSD\\ L\cdot C& =1+MSD-1VSD\\ & =1-0.95\\ & =0.05mm\end{array}$

$\begin{array}{cc}\therefore \text{Zero error}& =-1+7\times 0.05\\ & =-0.65mm\end{array}$