Q 11-01-037JEE MainMedium
A screw gauge has a pitch of $0.5\ \text{mm}$ and 50 divisions on its circular scale. It has a positive zero error of 3 circular divisions. While measuring the diameter of a wire, the main scale reading is $1.5\ \text{mm}$ and the circular scale reading is 36 divisions. Find the corrected diameter of the wire in mm.
Numerical value type. Enter your answer.
Answer: 1.83
Least count $= \dfrac{\text{pitch}}{\text{number of circular divisions}} = \dfrac{0.5}{50} = 0.01\ \text{mm}$
Observed reading $= 1.5 + 36\times 0.01 = 1.86\ \text{mm}$
Zero error $= +3\times 0.01 = +0.03\ \text{mm}$, which is subtracted:
$$d = 1.86 - 0.03 = 1.83\ \text{mm}$$
Solution by Sreeraj P, M.Sc Physics