Question

A thin plastic ring of radius $R$ carries a charge $q$ uniformly spread over the entire ring. The ring is rotating with angular velocity $\omega $ about its axis. The magnetic induction at the centre of the ring is

• A. $\frac{\mu _{0} q \omega }{2 \pi R}$
• B. $\frac{\mu _{0} q \omega }{\pi R}$
• C. $\frac{\mu _{0} q \omega }{4 \pi R}$
• D. zero

Answer 1

Answer: (C)

Due to charge $q$ moving on circular path
$B_{c e n t r e}=\frac{µ_{0} I}{2 R}=\frac{µ_{0} q f}{2 R}=\frac{µ_{0} q \omega }{4 \pi R}$