When does a charged circular loop behave as a point charge.

Under what condition a charged circular loop behaves as a point-charge in respect of electric field due to it?

A charged object can be treated as a point charge when

A charge Q is uniformly distributed over a ring of radius a.Obtain an expression for electric field intensity at a point on the axis of ring. show that at far point ring behaves as a point charge.

A thin circular ring of radius r is charged uniformaly so that its linear charge density becomes lambda . Derive an expression for the electric for the electric field at a point P at a distance x from it along the axis of the ring. Hence, prove that at large distances (x>>r), the ring behaves as a point charge.

How does a current loop behave like a bar magnet?