Question

In a vernier calipers $10$ smallest divisions of the vernier scale are equal to $9$ smallest divisions of the main scale. If the smallest division of the main scale is half millimeter, then the vernier constant is:

• A. $0.005\text{mm}$
• B. $0.05\text{mm}$
• C. $0.5\text{mm}$
• D. $0.01\text{mm}$

Answer 1

The correct option is B $0.05\text{mm}$

$MSD$ = Main scale divisions
$VSD$ = Vernier scale divisions
From the data given in the question,
$1MSD=0.5\text{mm}$ and, $10VSD=9MSD$
$\Rightarrow 1VSD=\frac{9}{10}MSD=\frac{9}{10}\times 0.5=0.45\text{mm}$
Vernier constant$\left(VC\right)$ or Least count$\left(LC\right)$,
$=1MSD-1VSD=0.5-0.45=0.05\text{mm}$
Hence, option (b) is the correct answer.