The bob of a simple pendulum is replaced by a magnet. The oscillations are set along the length of the magnet. $A$ copper coil is added so that one pole of the magnet passes in and out of the coil. The coil is short-circuited. Then which one of the following happens?

$A$ circular coil of $500$ turns of wire has an enclosed area of $0.1\,m^2$ per turn. It is kept perpendicular to a magnetic field of induction $0.2\,T$ and rotated by $180^o$ about a diameter perpendicular to the field in $0.1\,s$. How much charge will pass when the coil is connected to a galvanometer with a combined resistance of $50\,\Omega$?

The figure shows three circuits with identical batteries,inductors,and resistors. Rank the circuits according to the current through the battery $(i)$ just after the switch is closed and $(ii)$ a long time later,greatest first.

Two metallic rings $A$ and $B$,identical in shape and size but having different resistivities $\rho_A$ and $\rho_B$,are kept on top of two identical solenoids as shown in the figure. When current $I$ is switched on in both the solenoids in an identical manner,the rings $A$ and $B$ jump to heights $h_A$ and $h_B$,respectively,with $h_A > h_B$. The possible relation$(s)$ between their resistivities and their masses $m_A$ and $m_B$ is(are):
$(A)$ $\rho_A > \rho_B$ and $m_A = m_B$
$(B)$ $\rho_A < \rho_B$ and $m_A = m_B$
$(C)$ $\rho_A > \rho_B$ and $m_A > m_B$
$(D)$ $\rho_A < \rho_B$ and $m_A < m_B$

$A$ long straight wire is parallel to one edge of a rectangular loop as shown in the figure. If the current in the long wire varies with time as $I = I_0 e^{-t/\tau}$,what will be the induced $emf$ in the loop?

Assertion: $A$ current continues to flow in a superconducting coil even after the switch is off.
Reason: Superconducting coils show the Meissner effect.