Question

Identical charges (–q) are placed at each corner of a cube of side 'b' then electrical potential energy of charge (+q) which is placed at centre of cube will be

• A. $\frac{-4\sqrt2q^2}{\pi \epsilon_0b}$
• B. $\frac{-8\sqrt2q^2}{\pi \epsilon_0b}$
• C. $\frac{-4q^2}{\sqrt3\pi \epsilon_0b}$
• D. $\frac{8\sqrt2q^2}{4\pi \epsilon_0b}$

Answer 1

Answer: (C)

$\frac{-4q^2}{\sqrt3\pi \epsilon_0b}$

Answer 2

The correct option is (C) : $\frac{-4q^2}{\sqrt3\pi \epsilon_0b}$

E.P.E = 8[$\frac{1}{4}$π$\epsilon_0$×(q)(-q)/√3b/2]=$\frac{-4q^2}{\sqrt3\pi \epsilon_0b}$

Note : distance between centre to any corner = $\sqrt{\frac{3b}{2}}$