The induction coil works on the principle of

$A$ small square loop of wire of side $\ell$ is placed inside a large square loop of wire of side $L$ $(L \gg \ell)$. The loops are coplanar and their centers coincide. The value of the mutual inductance of the system is $\sqrt{x} \times 10^{-7} \text{ H}$, where $x = \dots$

If the current $30 \,A$ flowing in the primary coil is made zero in $0.1 \,s$,the $e.m.f.$ induced in the secondary coil is $1.5 \,V$. The mutual inductance between the coils is.....$H$.

$A$ transformer works on the principle of

Two circular coils can be arranged in any of the three situations shown in the figure. Their mutual inductance will be

Two coils $P$ and $S$ have a mutual inductance of $\pi \text{ mH}$. The secondary coil $S$ has resistance $4 \text{ } \Omega$ and self-inductance $(60/\pi) \text{ mH}$. If the current in the primary is $I_p = 12 \sin(50\pi t)$, then the maximum value of the current induced in coil $S$ is [Take $\pi^2 = 10$] (in $\text{ A}$)