When both jaws of vernier callipers touch each other, zero mark of the vernier scale is right to zero mark of main scale, 4th mark on vernier scale coincides with certain mark on the main scale. While measuring the length of a cylinder, observer observes 15 divisions on main scale and 5th division of vernier scale coincides with a min scale division. Measured length of cylinder i $s ______$ mm. (Least count of Vernier calliper = 0.1 mm)
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Question

When both jaws of vernier callipers touch each other, zero mark of the vernier scale is right to zero mark of main scale, 4th mark on vernier scale coincides with certain mark on the main scale. While measuring the length of a cylinder, observer observes 15 divisions on main scale and 5th division of vernier scale coincides with a min scale division. Measured length of cylinder i $s ______$ mm. (Least count of Vernier calliper = 0.1 mm)

Options

G1 Physics · Accepted Answer

When the jaws are closed, the vernier zero lies to the right of the main-scale zero. Hence the instrument has a positive zero error. The 4th vernier division coincides, so zero error = 4×LC = 4×0.1 = 0.4 mm. For the cylinder measurement, main-scale reading = 15 mm. Vernier coincidence is the 5th division: vernier reading = 5×0.1 = 0.5 mm. Observed reading is 15+0.5 = 15.5 mm. Corrected reading is observed reading - positive zero error = 15.5-0.4 = 15.1 mm. Correct option: B.