In the following diagrams a particle with small charge `-q` is free to move up or down , but not sideways near a larger fixed charge `Q`.The small charge is in equilibrium because in the positions shown ,the electrical upward force is equal to the weight of the particle .Which statement os true?

Options

A. In fig.`(A) ,-q` is in stable equilibrium
B. In fig.`(A) ,-q` is in neutral equilibrium
C. In fig.`(B) ,-q` is in stable equilibrium
D. Neither in fig.`A` nor in `B,-q` is in stable equilibrium

Answer

3

Explanation

In first diagram , if we displace `-q` in downward direction , electric force on it decreases , `mg != F_(e )` , it will move down (unstable equilibrium).
In second diagram , if we displace `-q` in downward direction , electric force on it increases , `F_(e ) gt mg` , net force restores `-q` to its original position (unstable equilibrium).