Question

Initially the spheres A and B are at potentials V_A and V_B respectively. Now sphere B is earthed by closing the switch. The potential of A becomes

(a) 0

(b)  V_A

(c) V_A - V_B

(d) V_B

Answer 1

Correct option: (c) V_A - V_B

Explanation:

Initially potential difference between the spheres is V_A - V_B. Since earthing of B will make potential of B zero but potential difference will not change because potential difference between two concentric spheres depends only on the charge on the innersphere. 

Hence Final Potential Difference = Initial Potential Differences