Energy required to establish a current of $4 \ A$ in a coil of self-inductance $L = 200 \ mH$ is . . . . . . . (in $J$)

If the current of $I$ gives rise to a magnetic flux $\phi$ through a coil having $N$ turns,then the magnetic energy stored in the medium surrounding the coil is

$A$ coil of inductance $2\, H$ having negligible resistance is connected to a source of supply whose voltage is given by $V = 3t$ volt (where $t$ is in seconds). If the voltage is applied when $t = 0$,then the energy stored in the coil after $4\, s$ is ............ $J$.

An inductor may store energy in

$A$ current $2 \ A$ flows through a solenoid of self-inductance $3 \ mH$. The energy stored inside the solenoid is $.... \ mJ$.

When a current $I$ flows through a coil,it stores the energy $E_1$ in it. Now the current is reduced to $I/2$,the energy stored in the coil becomes $E_2$. The change in the energy is