Question

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

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

Answer 1

The correct option is D $r^2$

Magnetic moment of a coil of radius $r$ carrying current $i$ is equal to
$M=iAn$ [A is area of the coil, $x$ is no. of turns]
$=ni\pi r^2$
So, $M\propto r^2$