JEE Main · 2021 · 25 Jul 2021 · Shift 1 · Units & Measurement

The least count is $\frac{\text{pitch}}{\text{divisions}}=\frac{0.1}{100}=0.001$ cm. With the jaws closed the reference line of the first gauge stands at the circular division $5$, a zero error of $+5$ divisions, while on the second it stands at $92$, which is $8$ divisions short of a full turn and so a zero error of $-8$ divisions. Each observed reading is the true value shifted by that gauge's zero error, so the two students read

The main scale supplies $0.300$ cm in both cases, leaving circular scale readings of $27$ and $14$. The difference between the two circular scale readings is $13$.