Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : In Vernier calliper if positive zero error exists, then while taking measurements, the reading taken will be more than the actual reading. Reason (R) : The zero error in Vernier Calliper might have happened due to manufacturing defect or due to rough handling. In the light of the above statements, choose the correct answer from the options given below :

Both (A) and (R) are correct but (R) is not the correct explanation of (A)

Both (A) and (R) are correct and (R) is the correct explanation of (A)

Units and Measurements PYQ — JEE Main 2024 · 27 Jan · Shift 2 · Q61 with Solution

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Correct answer: B

Analyze Assertion (A):
In a Vernier caliper, positive zero error means that when the jaws are fully closed, the zero of the Vernier scale lies to the right of the zero of the main scale. Hence the instrument shows a positive reading even when the actual length is zero.

Therefore, for any object measured, $\text{Observed reading} = \text{Actual reading} + \text{Positive zero error}$ So, the reading taken is more than the actual reading.

Hence, Assertion (A) is true.
Analyze Reason (R):
Zero error in a Vernier caliper can indeed occur due to:
- manufacturing defect,
- wear and tear,
- rough handling,
- improper alignment of jaws.
Hence, Reason (R) is also true.
Check whether (R) explains (A):
Assertion (A) is about the effect of positive zero error on measurement: it makes the observed reading larger than the true reading.

Reason (R) only states the possible causes of zero error, such as manufacturing defect or rough handling. It does not explain why positive zero error makes the reading more than the actual reading.

Therefore, (R) is not the correct explanation of (A).
Conclusion:
Both (A) and (R) are true, but (R) is not the correct explanation of (A).

So, the correct option is: $\boxed{\text{B}}$

View written solutionFree

Correct answer: B

Analyze Assertion (A):
In a Vernier caliper, positive zero error means that when the jaws are fully closed, the zero of the Vernier scale lies to the right of the zero of the main scale. Hence the instrument shows a positive reading even when the actual length is zero.

Therefore, for any object measured, $\text{Observed reading} = \text{Actual reading} + \text{Positive zero error}$ So, the reading taken is more than the actual reading.

Hence, Assertion (A) is true.
Analyze Reason (R):
Zero error in a Vernier caliper can indeed occur due to:
- manufacturing defect,
- wear and tear,
- rough handling,
- improper alignment of jaws.
Hence, Reason (R) is also true.
Check whether (R) explains (A):
Assertion (A) is about the effect of positive zero error on measurement: it makes the observed reading larger than the true reading.

Reason (R) only states the possible causes of zero error, such as manufacturing defect or rough handling. It does not explain why positive zero error makes the reading more than the actual reading.

Therefore, (R) is not the correct explanation of (A).
Conclusion:
Both (A) and (R) are true, but (R) is not the correct explanation of (A).

So, the correct option is: $\boxed{\text{B}}$