Question

The distance moved by the screw of a screw gauge is $2 \, mm$ in four rotations and there are $50$ divisions on its cap. When nothing is put between its jaws, $30^{th}$ division of circular scale coincides with the reference line, with zero of circular scale lying above the reference line. When a plate is placed between the jaws, the main scale reads $2$ divisions and the circular scale reads $20$ divisions. The thickness of the plate is

• A. $1.5 \, \text{mm}$
• B. $1.2 \, \text{mm}$
• C. $1.4 \, \text{mm}$
• D. $1.6 \, \text{mm}$

Answer 1

Answer: (A)

Pitch $= \frac{1}{2} \, \text{mm}$
least count $= \frac{0.5 \, \text{mm}}{50} = 0.01 \, \text{mm}$
Reading $= \left[\right. 2 \times \, \frac{1}{2} \, + 20 \times 0.01 \, - \left(\right. - 30 \times 0.01 \left.\right) \left]\right. = 1.5 \, \text{mm}$