A pendulum bob carries a -ve charge -q. A positive charge +q is held at the point of support. Then, the time period of the bob is:

Options

A. greater than `2pi sqrt(L//g)`
B. less than `2pi sqrt(L//g)`
C. equal to `2pi sqrt(L//g)`
D. equal to `2pi sqrt(2L//g)`

Answer

C

Explanation

There is no change in the restoring force as the electrostatic forces are the central forces. Negative and positive charges at the two extremities of the string affect tension T which does not affect the restoring force. Hence, time period of the bob will remain unchanged.
ie, `T=2pi sqrt((L)/(g))`