Question

A certain charge $Q$ is divided at first into two parts, $q$ and $Q - q$. Later on the charges are placed at a certain distance. If the force of interaction between two charges is maximum, then $Q/q$ =

• A. 4
• B. 2
• C. 1
• D. 0.5

Answer 1

Answer: (B)

2

Answer 2

$F \, \propto \, q (Q - q).$ For the force to be maximum. $dF/dq = 0 \, i.e., Q - 2q = 0 .$ $\therefore$ $q = Q/2$