Question

A ring of radius $R$ carries a uniformly distributed charge $+Q$. A point charge $-q$ is placed on the axis of the ring at a distance $2R$ from the centre of the ring and released from rest. The particle executes a simple harmonic motion along the axis of the ring.

• A. True
• B. False

Answer 1

The correct option is B False

Sine component of the force cancels out in pairs due to opposite particles in the ring.

So, cosine component of force dominates and the net force is in $-x$ direction when $-q$ charged particle is $+x$ direction and vice versa.

And there is symmetry in the electric force on the charge particle placed on the axis of ring due to charged ring. So charge particle will oscillate between $+2R$ and $-2R$ about the centre of the ring.