Question

Four point charge -Q, -q, 2q and 2Q are placed, one at each corner of the square. The relation between Q and q for which the potential at the centre of the square is zero is:

• A. $Q=q$
• B. $Q=\frac{1}{q}$
• C. $Q=-q$
• D. $Q=-\frac{1}{q}$

Answer 1

The correct option is C $Q=-q$

Four point charges $-Q,-q,2q,2Q$.

When it is in the potential at the centre of the square $=0$

then $Q=-q$.