Question

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 center of the ring is

• A. $\frac{\mu_0 qf}{2\pi R}$
• B. $\frac{\mu_0 qf}{2 R}$
• C. $\frac{\mu_0 q}{2 \, fR}$
• D. $\frac{\mu_0 q}{2\pi fR}$

Answer 1

Answer: (B)

$\frac{\mu_0 qf}{2 R}$

Answer 2

$B =\frac{\mu_{0} I }{2 R }=\frac{\mu_{0} qf }{2 R }$
$I =\frac{ q }{ T }= qf$