The total emf induced in a closely wound coil of $N$ turns in which the magnetic flux linked with the coil is changing at the rate $\frac{d \phi_{B}}{dt}$ is

$A$ coil of resistance $200 \Omega$ is placed in a magnetic field. If the magnetic flux $\phi$ (in weber) linked with the coil varies with time $t$ (in second) as per the equation $\phi = 50t^2 + 4$,then the current induced in the coil at a time $t = 2 \ s$ is (in $A$)

Consider a metal ring kept (supported by a cardboard) on top of a fixed solenoid carrying a current $I$ as per the figure. The centre of the ring coincides with the axis of the solenoid. If the current in the solenoid is switched off,what will happen to the ring?

The figure shows the north pole of a magnet moving away from a thick conducting loop containing a capacitor. The excess positive charge will arrive on

$A$ coil of resistance $400\,\Omega$ is placed in a magnetic field. If the magnetic flux $\phi$ (in $Wb$) linked with the coil varies with time $t$ (in $s$) as $\phi = 50t^2 + 4$,the current in the coil at $t = 2\,s$ is $..........\,A$.

Out of the following,which law obeys the law of conservation of energy?