Question

# Two points have a potential difference of 10 V. After connecting a conductor with zero resistance between the points, the final potential at each point becomes 25 V. What could be their initial potentials?

A
25V and 35V
B
20V and 30V
C
30V and 40V
D
35V and 45V

Solution

## The correct option is B 20V and 30VLet the points be denoted by A and B, and let VA>VB, where VA and VB denote the potentials at A and B respectively. The potential difference is defined as the difference in potential between A and B. ⇒VA−VB=10V Now, when a conductor with zero resistance connects A and B, the point with lower potential tends to increase its potential and the point with higher potential tends to decrease its potential by the same amount. In this case, the amount by which the potentials at A and B change is half their initial potential difference. So, VB increases by 5 V and VA  decreases by 5 V. Hence, VB will be 25−5=20 V And, VA will be 25+5=30 V

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