A charge Q is disturbed over three concentric spherical shells of radii a, b, c (a such that their surface charge densities are equal to one another. The total potential at a point at distance r from their common centre, where r a, would be : 

(a) 

(b) 

(c) 

(d) 

A charge Q is disturbed over three concentric spherical shells of radii a, b, c (a such that their surface charge densities are equal to one another. The total potential at a point at distance r from their common centre, where r a, would be : 

(a) 

(b) 

(c) 

(d) 

Potential at point P, V= + +
Q
= Q
= Q
V=
Correct answer is (b).