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

$A$ coil having effective area $A$ is held with its plane normal to a magnetic field of induction $B$. The magnetic induction is quickly reduced by $25 \%$ of its initial value in $2 \ s$. The e.m.f. induced across the coil will be:

$A$ long solenoid of radius $2\, cm$ has $100\, turns/cm$ and carries a current of $5\, A$. $A$ coil of radius $1\, cm$ having $100\, turns$ and a total resistance of $20\, \Omega$ is placed inside the solenoid coaxially. The coil is connected to a galvanometer. If the current in the solenoid is reversed in direction,find the charge flown through the galvanometer.

The magnetic flux linked with a coil at any instant $t$ is given by $\phi = 5t^3 - 100t + 300$. The $e.m.f.$ induced in the coil at $t = 2 \ s$ is $....... \ V$.

$A$ coil having $500$ square loops each of side $10\, cm$ is placed normal to a magnetic flux which increases at the rate of $1.0\, T/s$. The induced $e.m.f.$ in volts is:

Lenz's law is expressed by the following formula (here $e$ = induced $e.m.f.$,$\phi$ = magnetic flux in one turn and $N$ = number of turns).