Question

In a vernier callipers, smallest division on the main scale is $1mm$, while the vernier scale have $20$ divisions. When fixed jaw touches with movable jaw, zero of vernier scale lies on the right of the zero of the main scale and $15th$ division of vernier scaled coincides with any division of main scale. What is the type of zero error and its value?

• A. Positive, $0.75mm$
• B. Negative, $0.75mm$
• C. Positive, $0.15mm$
• D. Negative, $0.15mm$

Answer 1

The correct option is A Positive, $0.75mm$

$1MSD=1mm$

$\begin{array}{c}\text{(+)ive zero error}\\ \text{let}\\ nMSD=20VSD\\ \Rightarrow 1VSD=\frac{n}{20}MSD\\ \therefore LC=1\mathrm{MSD}-1VSD\\ =1-\frac{n}{20}mm\end{array}$

$\text{zero error}=+15\times L.C$

$\begin{array}{c}={lim}_{+15(1-\frac{n}{20})}\\ =15(1-\frac{31}{4}).\\ \text{if}n=19\end{array}$

$\text{Zero error}=+0,75mm$