Two concentric circular loops of radii $r _{1}=30\,cm$ and $r_{2}=50\,cm$ are placed in $X - Y$ plane as shown in the figure. $A$ current $I=7\,A$ is flowing through them in the direction as shown in figure. The net magnetic moment of this system of two circular loops is approximately.
JEE MAIN 2022, Medium
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$\overrightarrow{ M }=- i \pi(0.5)^{2} \hat{ k }+ i \pi(0.3)^{2} \hat{ k }$
$\overrightarrow{ M }=-7 \times \frac{22}{7}\left(\frac{25}{100}-\frac{9}{100}\right) \hat{ k }$
$=-22\left(\frac{16}{100}\right) \hat{ k }$
$\overrightarrow{ M }=-3.52 \hat{ k }\,Am ^{2}$
$=-\frac{7}{2} \hat{ k }\,Am ^{2}$
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