Question

An electron moves with a constant speed v along a circle of radius r. The magnetic moment will be (e is the electron charge).

• A. evr
• B. $\frac{1}{2}evr$
• C. $\pi r^{2}ev$
• D. $2\pi rev$

Answer 1

The correct option is B $\frac{1}{2}evr$

magnetic moment
$=niA$
$=\left(1\right)\frac{e}{t}\pi r^2$
$=\frac{ew}{2\pi }\pi r^2$ $(\because t=\frac{2\pi }{w})$
$=\frac{evr}{2}$ $(\because v=wr)$