Question

 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:  

 A) 0. 15 volt 

B) 0.15 volt  

C) 0.5 volt                  

D) ? 0.05 volt

Answer 1

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=220 cm, voltmeter reading

=0.0025x220=0.55V

Error=0.5-0.55 =-0.05V