Question

A given vernier callipers has 20 divisions on its vernier scale which coincide with 19 divisions of the main scale. The main scale has been graduated in mm. 

The positions, of the ‘zeros’ of its main scale and its vernier scale, when its jaws just touch one another, are as shown in the figure. 

For a given sphere, a student notes that the readings of the main scale, of the above vernier calliper is 2.4 cm while the 14th division of the vernier coincides with a main scale division. The diameter of this sphere, as per this reading, is

(1) 2.41 cm

(2) 2.53 cm

(3) 2.44 cm

(4) 2.50 cm

Answer 1

(3) 2.44 cm

The least count of the given vernier = 1/20 mm = 0.05 mm

Zero error = + 6 x L.C = 6 x 0.05 mm = 0.3 mm = 0.03 cm 

Observed reading,

= [2.4 + (14 x 0.05)x10^-1] cm

= 2.47 cm

∴ Corrected reading = (2.47- 0.03) cm = 2.44 cm