A galvanometer of resistance 50 Ω has 25 scale divisions. A current of 4 × 10⁻⁴ A gives one division deflection. To convert it into a voltmeter of full-scale range 25 V, which external resistance should be used?
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Question

A galvanometer of resistance 50 Ω has 25 scale divisions. A current of 4 × 10⁻⁴ A gives one division deflection. To convert it into a voltmeter of full-scale range 25 V, which external resistance should be used?

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G1 Physics · Accepted Answer

Step 1: Calculate galvanometer full-scale current I(g) = 25 divisions × (4×10⁻⁴ A/division) = 0.010 A. Step 2: For a voltmeter, required series resistance R(series) = V(range)/I(g) − G. Step 3: For the source's voltage range of 25 V, R(series)=25/0.01−50=2450 Ω; add IN SERIES. Answer D, correcting previous import B. Final answer: (D) 2450 Ω in series.