JEE Main 2014 · 12 Apr · Shift 1 · Physics Q30

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In the experiment of calibration of voltmeter, a standard cell of e.m.f. 1.1 volt is balanced against 440 cm of potentiometer wire. The potential difference across the ends of resistance is found to balance against 220 cm of the wire. The corresponding reading of voltmeter is 0.5 volt. The error in the reading of voltmeter will be :

−0.15 volt

0.15 volt

0.5 volt

−0.05 volt

Answer and worked solution

Official answer: D

Potential gradient: $\frac{1.1}{440}$ V/cm. The true p.d. is $\frac{1.1}{440}\times220=0.55$ V.

Error = reading − true value $=0.5-0.55=-0.05$ V.

Topics:Potentiometer

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JEE Main 2014 · 12 Apr · Shift 1, Physics question 30