Q. A charge $Q$ is divided into two parts of $q$ and $Q - q$. If the coulomb repulsion between them when they are separated is to be maximum, the ratio of $\frac{Q}{q}$ should be
A) 2
B) $1/2$
C) 4
D) $1/4$
Explanation
(a) Let separation between two parts be $r \Rightarrow F = \ k.q\frac{(Q - q)}{r^{2}}$
For $F$ to be maximum $\frac{dF}{dq} = 0 \Rightarrow \frac{Q}{q} = \frac{2}{1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.