A sphere of radius R contains a total charge +Q which is uniformly distributed throughout its volume. At a distance 2R from the centre of sphere, a particle having charge +q is fixed. P is a point on surface of sphere and lying on line joining the centre of sphere and point charge. For what value of q will the electric field at P be zero.
(A) Q / 2
(B) Q
(C) 5 / 7 Q
(D) 2Q
