Question

The least count of the main scale of a vernier callipers is 1 mm. Its vernier scale is divided into 10 divisions and coincide with 9 divisions of the main scale. When jaws are touching each other, the 7^th division of vernier scale coincides with a division of main scale and the zero of vernier scale is lying right side of the zero of main scale. When this vernier is used to measure length of cylinder the zero of the vernier scale between 3.1 cm and 3.2 cm and 4^th VSD coincides with a main scale division. The length of the cylinder is (VSD is vernier scale division) 

(1) 2.99 cm 

(2) 3.07 cm 

(3) 3.21 cm 

(4) 3.2 cm

Answer 1

Ans. (2) 3.07 cm

Sol. Zero Error = 0 + 7 × 0.1 = 0.070 

Vernier reading = (3.1 + 4 × 0.01) – 0.07 = 3.07