Charge q is uniformly spreade 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

Options

A. `(mu_0qf)/(2 piR)`
B. `(mu_0qf)/(2R)`
C. `(mu_0q)/(2fR)`
D. `(mu_0q)/(2pi fR)`

Answer

B

Explanation

The current following in the ring is
The magnetic induction at the centre of the ring is
`B = (mu_0 2pil)/(4pi R) = (mu_0 qf)/(2R)`