Q. A straight wire carrying current $i$ is turned into a circular loop. If the magnitude of magnetic moment associated with it in M.K.S. unit is $M$, the length of wire will be
A) $4\pi iM$
B) $\sqrt{\frac{4\pi M}{i}}$
C) $\sqrt{\frac{4\pi i}{M}}$
D) $\frac{M\pi}{4i}$
Explanation
(b) Magnetic moment of circular loop carrying current
$M = IA = I\left( \pi R^{2} \right) = I\pi\left( \frac{L}{2\pi} \right)^{2} = \frac{IL^{2}}{4\pi} \Rightarrow L = \sqrt{\frac{4\pi M}{I}}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.