Two loops with sides L and l (L >> l) are placed concentrically and coplanar as shown in figure. The mutual inductance of the system is proportional to
Answer & explanation
Correct answer: option 4
The value of B is given by Bigger loop at the centre is given by
$B = \frac{2\sqrt 2 \mu_0 I}{\pi L}$
The flux linked with the smaller loop
$ \phi = M I = BA = Bl^2$
$\Rightarrow MI = \frac{2\sqrt 2 \mu_0 Il^2}{\pi L}$
$M \propto \frac{l^2}{L}$