If a current of $3.0$ $amperes$ flowing in the primary coil is reduced to zero in $0.001$ $second,$ then the induced $e.m.f$ in the secondary coil is $15000$ $volts$. The mutual inductance between the two coils is....$henry$

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

A small square loop of wire of side $l$ is placed inside a large circular loops of radius $r$. The loop are coplanar and their centre coincide. The mutual inductance of the system is proportional to

In a $dc$ motor, induced $e.m.f.$ will be maximum

Two coil $A$ and $B$ have coefficient of mutual inductance $M = 2H$. The magnetic flux passing through coil $A$ changes by $4$ Weber in $10$ seconds due to the change in current in $B$. Then

The mutual inductance of a pair of coils, each of $N\,turns$, is $M\,henry$. If a current of $I\, ampere$ in one of the coils is brought to zero in $t$ $second$ , the $emf$ induced per turn in the other coil, in volt, will be