Physics - Electrostatics Question with Solution | TestHub

Let the side length of square be ‘a’ then potential at center O is

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



$=-Q-q+2q+2Q=0\Rightarrow Q+q=0$

$\Rightarrow Q=-q$