Two coils of self-inductances $2\, mH$ and $8\, mH$ are placed so close together that the effective flux in one coil is completely linked with the other. The mutual inductance between these coils is......$mH$.

An alternating current with an angular frequency of $\omega = 200\,rad/s$ and a peak value of $I_0 = 1\,A$,as shown in the figure,is applied to the primary coil of a transformer. If the coefficient of mutual induction between the primary and the secondary coils is $M = 1.5\,H$,the magnitude of the induced voltage in the secondary coil will be.....$V$.

$AB$ is an infinitely long wire placed in the plane of a rectangular coil $PQRS$ with dimensions as shown in the figure. Calculate the mutual inductance of wire $AB$ and coil $PQRS$.

$A$ solenoid has $2000$ turns wound over a length of $0.3\,m$. The area of cross-section is $1.2\times10^{-3}\,m^2$. Around its central section,a coil of $300$ turns is closely wound. If an initial current of $1\,A$ is reversed in $0.25\,s$,find the emf induced in the coil in $mV$.

$A$ short solenoid (length $l$ and radius $r$ with $n$ turns per unit length) lies well inside and on the axis of a very long,coaxial solenoid (length $L$,radius $R$ and $N$ turns per unit length,with $R > r$). Current $I$ flows in the short solenoid. Choose the correct statement.

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 . . . . . . .