JEE Main 2014 · 6 Apr · Shift 1 · Physics Q30

PhysicsSingle correct+4 / -1Question 30 of 90

A student measured the length of a rod and wrote it as 3.50 cm. Which instrument did he use to measure it ?

A meter scale.

A vernier calliper where the 10 divisions in vernier scale matches with 9 division in main scale and main scale has 10 divisions in 1 cm.

A screw gauge having 100 divisions in the circular scale and pitch as 1 mm.

A screw gauge having 50 divisions in the circular scale and pitch as 1 mm.

Answer and worked solution

Official answer: B

3.50 cm is recorded to 0.01 cm $=0.1$ mm, the least count needed. A vernier with 10 VSD = 9 MSD and 1 MSD = 1 mm has least count $1-0.9=0.1$ mm.

A metre scale reads to 1 mm. The screw gauges read to 0.01 and 0.02 mm, so they would give more decimal places.

JEE Main 2014 · 6 Apr · Shift 1, Physics question 30