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{{\varepsilon }_{0}}r} $
• C. $ \frac{Qq}{2\pi G{{\varepsilon }_{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 {{\varepsilon }_{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.