If a current of $3.0 \ A$ flowing in the primary coil is reduced to zero in $0.001 \ s$,then the induced $e.m.f.$ in the secondary coil is $15000 \ V$. The mutual inductance between the two coils is (in $H$):

Two concentric circular coils,one of small radius $r_1$ and the other of large radius $r_2$,such that $r_1 \ll r_2$,are placed co-axially with their centres coinciding. The mutual inductance $M$ of the arrangement is proportional to . . . . . . .

Two conducting circular loops of radii $R_{1}$ and $R_{2}$ are placed in the same plane with their centres coinciding. If $R_{1} >> R_{2}$,the mutual inductance $M$ between them will be directly proportional to:

An $e.m.f.$ of $100 \, mV$ is induced in a coil when the current in another nearby coil changes from $0 \, A$ to $10 \, A$ in $0.1 \, s$. The coefficient of mutual induction between the two coils is . . . . . . $mH$.

$A$ primary coil and a secondary coil are placed close to each other. $A$ current, which changes at the rate of $25 \, A$ in a millisecond, is present in the primary coil. If the mutual inductance is $92 \times 10^{-6} \, H$, then the value of the induced emf in the secondary coil is:

Two concentric circular coils,one of small radius $r_1$ and the other of large radius $r_2$,such that $r_1 \ll r_2$,are placed coaxially with centers coinciding. Obtain the mutual inductance of the arrangement.