If a charge Q is divided into two charges q1 and q2, what is the magnitude of each charge to obtain maximum repulsion between them?
Answer & explanation
Correct answer: option 2
Use hit and trial method on the options. $Q_2 = Q - Q_1$
$ F = \frac{kQ_1 (Q-Q_1)}{d^2} = \frac{kQQ_1 - kQ_1^2}{d^2}$
For Maximum force $\frac{dF}{dQ_1} = 0$
$\Rightarrow Q_1 = Q -Q_1$
$ \Rightarrow Q_1 = \frac{Q}{2}$
$ Q_2 = Q_1 = \frac{Q}{2}$