Question

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

• A. $\frac{1}{r^2}$
• B. $\frac{1}{r}$
• C. $r$
• D. $r^2$

Answer 1

The correct option is D $r^2$

Magnetic moment of a current carrying wire is given by
$M=IA$
I is the current flowing in the wire and A is the area enclosed .
$A=\pi r^2$
$M=I\pi r^2$