Q. An electron of charge $e$ moves with a constant speed $v$ along a circle of radius $r$. Its magnetic moment will be
A) $evr$
B) $evr/2$
C) $\pi\ r^{2}ev$
D) $2\ \pi\ rev$
Explanation
(b) Here, area of circular orbit of electron, $A = \ \pi r^{2};$ current due to motion of electron
$i = \frac{e}{t} = \frac{e}{(2\pi r/v)} = \frac{ev}{2\pi r}$
$\therefore\ \ $Magnetic moment $= i\ A = \frac{ev}{2\pi r}\ \times \ \pi r^{2}$
$= \frac{e\ v\ r}{2}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.