Discussion Forum

Four point charges -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

Answer:

Explanation:

Let the side length of square be 'a' then potential at centre O is

$V = \frac{k (-Q)}{\left(\frac{a}{\sqrt{2}}\right)}+\frac{k (-q)}{\frac{a}{\sqrt{2}}}+\frac{k (2q)}{\frac{a}{\sqrt{2}}}+\frac{k (2Q)}{\frac{a}{\sqrt{2}}}$ =0

= -Q-q+2q+2Q = 0 → Q+q = 0 → Q = -q