If 8 identical charges of -g each are placed at the eight corners of a cube of side b, then electrostatic potential energy of a charge `+q_0` placed at the centre of the cube will be

Options

A. `(8 sqrt 2 q q_0)/(4pi epsi_0b)`
B. `-(8 sqrt 2 q q_0)/(4pi epsi_0b)`
C. `+ (4 q q_0)/(sqrt3pi epsi_0 b)`
D. `-(4 q q_0)/(sqrt3 pi epsi_0 b)`

Answer

D

Explanation

Distance of each corner of cube from its centre `r = (bsqrt3)/2`
` :.` Potential energy `u = 8[((-q)(q_0))/(4piepsi_0 r)] = -(4qq_0)/(sqrt3pi epsi_0b)`