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

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

The area of its cross-section is $1.2 \times {10^{ - 3}}{m^2}$. Around its central section, a coil of $300$ turns is wound. If an initial current of $2A$ in the solenoid is reversed in $0.25\, sec$, then the $e.m.f$. induced in the coil is

A small square loop of wire of side $l$ is placed inside a large square loop of wire of side $(L > l)$. The loop are coplanar and their centre coincide. The mutual inductance of the system is proportional to

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

What is the coefficient of mutual inductance when the magnetic flux changes by $2 \times {10^{ - 2}}\,Wb$ and change in current is $0.01\,A$......$henry$