Question

When both jaws of a vernier calipers touch each other, zero mark of the vernier scale is right to the zero mark of main scale. 4th mark on vernier scale coincides with a 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 main scale division. Measured length of cylinder is ________ mm. (Least count of Vernier calliper = \(0.1\) mm)

• A. \(15.4\)
• B. \(15.5\)
• C. \(15.9\)
• D. \(15.1\)

Hint:

Positive zero error is subtracted, while negative zero error is added to the observed reading.

Answer 1

The Correct Option is D

Concept: Measured reading using vernier calipers must be corrected for zero error. If the zero of the vernier scale lies to the {right} of the main scale zero, the zero error is {positive} and must be {subtracted} from the observed reading.
Step 1: Determine the zero error Given: - 4th vernier division coincides when jaws are closed - Least count \(=0.1\) mm \[ \text{Zero error} = +4 \times 0.1 = +0.4 \text{ mm} \]
Step 2: Find the observed reading Main scale reading: \[ 15 \text{ mm} \] Vernier scale reading: \[ 5 \times 0.1 = 0.5 \text{ mm} \] Observed reading: \[ 15 + 0.5 = 15.5 \text{ mm} \]
Step 3: Apply zero correction Since zero error is positive: \[ \text{Correct reading} = 15.5 - 0.4 = 15.1 \text{ mm} \]