Question

Two circular current carrying coils of radius $3\text{cm}$ and $6\text{cm}$ are having equal magnetic moment. Find the ratio of currents in the loops.

• A. $4:1$
• B. $9:1$
• C. $2:1$
• D. $1:3$

Answer 1

The correct option is A $4:1$

We know that magnetic moment,

$\mu =nIA$

$\Rightarrow \mu =1\times I\left(\pi R^2\right)\left[\text{For a circular loop}\right]$

For the same magnetic moment,

$I\propto \frac{1}{R^2}$

$\Rightarrow \frac{I_1}{I_2}=\frac{R_2^2}{R_1^2}=\frac{6^2}{3^2}=\frac{4}{1}=4:1$