Two small spheres, each carrying a charge q are placed r m apart and they interact with force F. If one of the sphere is taken around the other once in a circular path, the work done will be equal to

Options

A. `2pir^2`
B. `2pir`
C. `pir`
D. zero

Answer

D

Explanation

Electric force during the circular motion of the sphere remains perpendicular to its displacement all the time. Because at every instant displacement of the sphere is directed along the tangent to the circular path and electric force remains along radial direction. Hence, the net work done is zero.