Question

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

• A. $\frac{{\mu }_{0}qf}{2R}$
• B. $\frac{{\mu }_{0}q}{2fR}$
• C. $\frac{{\mu }_{0}q}{2\pi fR}$
• D. $\frac{{\mu }_{0}qf}{2\pi R}$

Answer 1

The correct option is A $\frac{{\mu }_{0}qf}{2R}$

$B=\frac{{\mu }_{0}I}{2R},$
$I=\frac{q}{T}=qf$

$B=\frac{{\mu }_{0}qf}{2R}$.