A circular loop ofradius $0.3\ cm$ lies parallel to amuch bigger circular loop ofradius $20\ cm$. The centre of the small loop is on the axis of the bigger loop. The distance between their centres is $15\ cm$. If a current of $2.0\ A$ flows through the smaller loop, then the flux linked with bigger loop is

$AB$ 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 $PQRS$

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

Two coils $A$ and $B$ having turns $300$ and $600$ respectively are placed near each other, on passing a current of $3.0$ ampere in $A$, the flux linked with A is $1.2 \times {10^{ - 4}}\,weber$ and with $B$ it is $9.0 \times {10^{ - 5}}\,weber$. The mutual inductance of the system is

The induction coil works on the principle of

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