Q 11-01-061JEE MainJEE Main 2026 (4 Apr, Shift 1)Easy
In a screw gauge when the circular scale is given five complete rotations it moves linearly by $2.5$ mm. If the circular scale has $100$ divisions, the least count of screw gauge is ______ mm.
Answer: (D) $5 \times 10^{-3}$
Concept. Pitch is the distance the spindle moves in one full rotation; the least count is the pitch divided by the number of circular divisions.
Step 1. Pitch.
$$p=\frac{2.5\ \text{mm}}{5}=0.5\ \text{mm}$$
Step 2. Least count.
$$\text{LC}=\frac{0.5}{100}=0.005\ \text{mm}=5\times10^{-3}\ \text{mm}$$
Answer. $5\times10^{-3}$ mm (Option D).
Solution by Sreeraj P, M.Sc Physics
