Question

A charge q is fixed. Another charge Q is brought near it and rotated in a circle of radius r around it. Work done during rotation is

• A. zero
• B. $\frac{Qq}{4\pi G{\epsilon }_{0}r}$
• C. $\frac{Qq}{2\pi G{\epsilon }_{0}r}$
• D. None of these

Answer 1

Answer: (A)

Potential due to charge $(q)$ at point $(r)$ is given by $V=\frac{1}{4\pi {\epsilon }_0}.\frac{q}{r}$
Since, charge $Q$ is rotated in a circle of radius $r$ , hence its potential remains same at all points on the path, hence $\Delta V=0$ . Also, work done
$=q\Delta V$ where $q$ is charge and $\Delta V=0$ .
$\therefore$ Work done = 0.