Charge q is uniformly spread on a thin ring of radius R.

Charge q is uniformly spread on a thin ring of radius R. The ring rotates about its axis with a uniform frequency f Hz. The magnitude of magnetic induction at the centre of the ring is

When the ring rotates about its axis with a uniform frequency f Hz, the current flowing in the ring is

I =	q	= qf
	T

Magnetic field at the centre of the ring is

B =	μ₀I	=	μ₀qf
	2R		2R