Question

The magnetic moment of a current $(I)$ carrying circular coil of radius $(r)$ and number of turns $(n)$ varies as

• A. $1/r^2$
• B. $1/r$
• C. $r$
• D. $r^2$

Answer 1

Answer: (D)

The magnetic moment is a measure of the strength of a magnetic source. The equation for magnetic moment in the current carrying loop, carrying current $I$ and of area vector $A$ for which the magnitude is given by
$M=IA$
where $I$ is current $A$, is area $\left(=\pi r^2\right)$
$\therefore M=I\pi r^2$
$\Rightarrow M\propto r^2$