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

$A$ small square loop of wire of side $l$ is placed inside a large square loop of wire $L$ $(L \gg l)$. Both loops are coplanar and their centres coincide at point $O$ as shown in the figure. The mutual inductance of the system is:

The mutual inductance between a primary and secondary circuit is $0.5 \, H$. The resistances of the primary and the secondary circuits are $20 \, \Omega$ and $5 \, \Omega$ respectively. To generate a current of $0.4 \, A$ in the secondary,the current in the primary must be changed at the rate of . . . . . . $A/s$.

$A$ small square loop of wire of side $l$ is placed inside a large square loop of side $L$ $(L \gg l)$. If the loops are coplanar and their centres coincide,the mutual inductance of the system is directly proportional to :

$A$ long straight wire is placed along the axis of a circular ring of radius $R$. The mutual inductance of this system is

In a transformer, the coefficient of mutual inductance between the primary and the secondary coil is $0.2 \, H$. When the current changes by $5 \, A/s$ in the primary, the induced $e.m.f.$ in the secondary will be......$V$