A solid sphere of radius R has charge q uniformly distributed over its volume. The distance from it surfce at which the electrostatic potential is equal to half of the potential at the centre is

Options

A. R
B. `R//2`
C. `R//3`
D. `2R`

Answer

c

Explanation

`(k Q)/(x) = (1)/(2) ((3)/(2) (k Q)/r)` or `x = 4 R // 3`
Distance from surface is `x - R = R//3`.