Q 12-01-114JEE MainJEE Main 2021 (20 Jul, Shift 1)Easy
A certain charge $Q$ is divided into two parts $q$ and $(Q - q)$. How should the charges $Q$ and $q$ be divided so that $q$ and $(Q - q)$ placed at a certain distance apart experience maximum electrostatic repulsion?
Answer: (B) $Q = 2q$
$F \propto q(Q - q)$. Setting $\dfrac{dF}{dq} = Q - 2q = 0$ gives $q = \dfrac{Q}{2}$, i.e. $Q = 2q$.
Solution by Sreeraj P, M.Sc Physics