Electric field is the electrostatic force per unit charge acting on a vanishingly small test charge placed at that point. It is a vector quantity and the electric field inside a charged conductor is zero. Electric flux `phi` is the total number of electric lines of force passing through a surface in a direction normal to the surface when the surface is placed inside the electric field.
`phi=ointvecE.vec(ds)=q/epsilon_0`
A positive charge Q is uniformly distributed along the circular ring of radius R. A small test charge q is placed at the centre of te ring as shown.

Options

A. If qgt0 and is displaced away from the centre is the plane of the ring it will be pushed back towards the centre.
B. If qlt0 and is displaced away from the centre in the plane of the ring. It will never return to the centre and will continue moving till it hits the ring.
C. If qlt0, it will perform SHM for small displacement along the axis.
D. q at the centre of the ring is an unstbae equilibrium within the plane of the ring for qgt0.