Question

A vernier callipers has 1 mm marks on the main scale. It has 20 equal divisions on the Vernier scale which match with 16 main scale divisions. For this Vernier callipers, the least count is:
A. 0.02 m
B. 0.05 mm
C. 0.1 mm
D. 0.2 mm

Answer 1

Least count means smallest length that can be measured using an instrument.

A vernier callipers has two scales:

1. The main scale

2.The vernier scale.

Now we know that Least count = 1 main scale division - 1 vernier scale division

Generally in a vernier callipers N main scale divisions coincide with N-1 vernier scale divisions.

But acc to our question,

20 VSD coincides with 16 MSD

Therefore, Least Count = 1 MSD - 1VSD = 1mm - (16/20)*1mm = 4/20 mm = 0.2mm that is option D.

Hence the Least Count of the Vernier Callipers is 0.2 mm

Answer 2

option is d

Explanation:

1 MSD =1 mm

20 VSD = 16 MSD

1 VSD = 16/20 MSD

1 VSD = 4/5MSD

LC = 1MSD - 1VSD

= 1MSD-4/5MSD

= (1-4/5)MSD

= 1/5 MSD

= 1MSD/5

= 0.2mm