Question

A vernier callipers has its main scale of $10cm$ equally divided into $200$ equal parts. Its vernier scale of $25$ divisions coincides with $12mm$ on the main scale. The least count of the instrument is -

• A. $0.020cm$
• B. $0.002cm$
• C. $0.010cm$
• D. $0.001cm$

Answer 1

The correct option is B $0.002cm$

$10cm$ of Main Scale $=200$ div of Main scale

$\Rightarrow IMSD=0.05cm$

given $25$ vernier scale division coincide with $12mm$ on main scale

$\Rightarrow 25VSD=12mm$ on main scale

$=\frac{12}{0.5}=24MSD$

$\Rightarrow 25VSD=24MSD$

$\Rightarrow 1VSD=\frac{24}{25}MSD=0.048cm$

Least Count $\Rightarrow 1MSD-1VSD$

$\Rightarrow (0.050-0.048)cm$

$\Rightarrow 0.002cm$