Question

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 error in the reading of voltmeter will be :

• A. $-0.15$ volt
• B. $0.15$ volt
• C. $0.5$ volt
• D. $-0.05$ volt

Answer 1

The correct option is D $-0.05$ volt

If we have to find out the error of voltmeter if the same is showing $0.5V$, then answer is D.
Potential per unit length $=1.1/440=0.0025V/cm$
For length $l=220cm$, voltmeter reading $=0.0025\times 220=0.55V$
Error $=0.5-0.55=-0.05V$