In the experiment of calibration of voltmeter, a standard cell of e.m.f. 1.1 volt is balanced against 440 cm of potential wire. The potential difference across the ends of resistance is found to balan

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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 potential 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 volmeter will be:

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In a voltmeter V ∝ l V = k l ​ Now, it is given E = 1.1 volt for l 1 ​ = 440 cm and V = 0.5 volt for l 2 ​ = 220 cm Let the error in reading of voltmeter be Δ V then, ​ 1.1 = 400 K and ( 0.5 − Δ V ) = 220 K . ⇒ 440 1.1 ​ = 220 0.5 − Δ V ​ ∴ Δ V = − 0.05 volt ​

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