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

$A$ circular loop of radius $0.3 \ cm$ lies parallel to a much bigger circular loop of radius $20 \ cm$. The centre of the smaller 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 the bigger loop is $............. \times 10^{-11} \ Wb$.

Find the mutual inductance in the arrangement,when a small circular loop of wire of radius $R$ is placed inside a large square loop of wire of side $L$ $(L \gg R)$. The loops are coplanar and their centres coincide:

$A$ circular wire loop of radius $R$ is placed in the $x$-$y$ plane centered at the origin $O$. $A$ square loop of side $a$ $(a \ll R)$ having two turns is placed with its center at $z = \sqrt{3} R$ along the axis of the circular wire loop,as shown in the figure. The plane of the square loop makes an angle of $45^{\circ}$ with respect to the $z$-axis. If the mutual inductance between the loops is given by $\frac{\mu_0 a^2}{2^{p / 2} R}$,then the value of $p$ is

The coefficient of mutual induction is $3 \text{ H}$ and induced e.m.f. across secondary is $4 \text{ kV}$. Current in primary is reduced from $7 \text{ A}$ to $2 \text{ A}$. The time required for the change of current is

Two coils of self-inductances $2\, mH$ and $8\, mH$ are placed so close together that the effective flux in one coil is completely linked with the other. The mutual inductance between these coils is......$mH$.