Question

A small charge q is rotated in a complete circular path of radius r surrounding another charge Q. The work done in this process is _________

(a) Zero

(b) \(\frac {qQ}{4\pi \varepsilon r}\)

(c) \(\frac {q}{4\pi \varepsilon (\pi r)}\)

(d) \(\frac {q}{4\pi \varepsilon (2\pi r)}\)

This question was addressed to me during a job interview.

My query is from Electrostatic Potential due to a Point Charge topic in chapter Electrostatic Potential and Capacitance of Physics – Class 12

Answer 1

The correct option is (a) Zero

For explanation I would say: We know that electric potential does not depend on the path, i.e. it is a state function. Therefore if we rotate a charge around another in a complete circular path, the potential energy of its initial and final points is the same. Therefore, there is no change of potential energy of the charge and hence net work done on the charge is zero.