In the figure,the switch $S$ is closed so that a current flows in the iron-core inductor which has inductance $L$ and the resistance $R$. When the switch is opened,a spark is obtained at the contacts. The spark is due to

If an iron rod is placed inside a coil, what happens to the induced current?

The adjoining figure shows two different arrangements in which two square wire frames are placed in a uniform constantly decreasing magnetic field $B.$ If $I_1$ and $I_2$ are the magnitudes of induced current in the cases $I$ and $II$,respectively,then

$A$ flexible wire bent in the form of a circle is placed in a uniform magnetic field perpendicular to the plane of the coil. The radius of the coil changes as shown in the figure. The graph of induced $emf$ in the coil is represented by

$A$ coil having $N$ turns and resistance $R$ $\Omega$ is connected to a galvanometer of resistance $6R$ $\Omega$. The magnetic flux linked with this coil changes from $\phi_1$ weber to $\phi_2$ weber in time $t$ second. The induced current in the circuit is

$A$ small circular loop of area $A$ and resistance $R$ is fixed on a horizontal $xy$-plane with the center of the loop always on the axis $\hat{n}$ of a long solenoid. The solenoid has $m$ turns per unit length and carries current $I$ counterclockwise as shown in the figure. The magnetic field due to the solenoid is in $\hat{n}$ direction. $List-I$ gives time dependences of $\hat{n}$ in terms of a constant angular frequency $\omega$. $List-II$ gives the torques experienced by the circular loop at time $t=\frac{\pi}{6\omega}$. Let $\alpha=\frac{A^2 \mu_0^2 m^2 I^2 \omega}{2R}$.

$List-I$	$List-II$
$(I)$ $\frac{1}{\sqrt{2}}(\sin \omega t \hat{j}+\cos \omega t \hat{k})$	$(P)$ $0$
$(II)$ $\frac{1}{\sqrt{2}}(\sin \omega t \hat{i}+\cos \omega t \hat{j})$	$(Q)$ $-\frac{\alpha}{4} \hat{i}$
$(III)$ $\frac{1}{\sqrt{2}}(\sin \omega t \hat{i}+\cos \omega t \hat{k})$	$(R)$ $\frac{3\alpha}{4} \hat{i}$
$(IV)$ $\frac{1}{\sqrt{2}}(\cos \omega t \hat{j}+\sin \omega t \hat{k})$	$(S)$ $\frac{\alpha}{4} \hat{j}$

Which one of the following options is correct?