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 figure. The mutual inductance of the system is.

There are two long co -axial solenoids of same length $l.$ The inner and outer coils have radii $r_1$ and $r_2$ and number of turns per unit length $n_1$ and $n_2$ respectively. The ratio of mutual inductance to the self -inductance of the inner -coil is

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....$henry$

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

A small square loop of side $'a'$ and one turn is placed inside a larger square loop of side ${b}$ and one turn $(b \gg a)$. The two loops are coplanar with thei centres coinciding. If a current $I$ is passed in the square loop of side $'b',$ then the coefficient of mutual inductance between the two loops is

The pointer of a dead-beat galvanometer gives a steady deflection because