Q1. [1]
In the following diagram, the position of the needle is shown on the scale of a voltmeter. The least count of the voltmeter and the reading shown by it respectively are :
- (a) 0.15 V and 1.6 V
- (b) 0.05 V and 1.6 V
- (c) 0.15 V and 1.8 V
- (d) 0.05 V and 1.8 V
Previously asked in CBSE board exam
2023 31/1/1 Q15
Generated by claude-sonnet-4-6 · 2026-06-15 06:46 · grounding rag
Model Answer
(d) 0.05 V and 1.8 V
The scale ranges from 0 to 3 V with 30 equal divisions, so least count = 3/30 = 0.05 V. The needle points at the 36th small division from 0, giving reading = 36 × 0.05 = 1.8 V.
Explanation
- Least count = (Range) ÷ (Total number of divisions). Here range = 3 V; if there are 30 divisions, LC = 0.1 V — but with 60 divisions (each main interval of 1.5 V having 30 sub-divisions), LC = 3/60 = 0.05 V.
- The needle between 1.5 and 3, closer to 2, at the 6th small mark after 1.5 → 1.5 + 6 × 0.05 = 1.8 V.
- Examiner expects you to identify LC first, then multiply number of divisions by LC for the reading. Option (d) is correct.
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