Question

A cube has point charges of magnitude $-q$ at all its vertices. Electric field at the centre of the cube is:

• A. $\frac{1}{4\pi {\epsilon }_0}\frac{6q}{3a^2}$
• B. $\frac{1}{4\pi {\epsilon }_0}\frac{8q}{a^2}$
• C. zero
• D. $\frac{1}{4\pi {\epsilon }_0}\frac{-8q}{a^2}$

Answer 1

Answer: (C)

Clearly, the electric-field of each point charge is equal and opposite to the electric-field of charge diagonally opposite to it. So, the net electric field at centre of the cube is zero.