A galvanometer having a resistance of 20 Ω and 30 divisions on both sides has figure of merit 0.005 ampere/division. The resistance that should be connected in series such that it can be used as a voltmeter upto 15 volt, is :-
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Question

A galvanometer having a resistance of 20 Ω and 30 divisions on both sides has figure of merit 0.005 ampere/division. The resistance that should be connected in series such that it can be used as a voltmeter upto 15 volt, is :-

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G1 Physics · Accepted Answer

Full-scale current is 30×0.005=0.15 A. A 15 V voltmeter therefore needs total resistance 15/0.15=100 Ω. Subtracting galvanometer resistance 20 Ω gives series resistance 80 Ω. Hence A.