The magnetic potential energy stored in a certain inductor is $49 \ mJ$ when the current in the inductor is $70 \ mA$. The inductance of the inductor is (in $H$)

Assertion : If the current in a solenoid is reversed in direction while keeping the same magnitude,the magnetic field energy stored in the solenoid remains unchanged.
Reason : Magnetic field energy density is proportional to the magnetic field.

In what form is the energy stored in an inductor?

The expression for the magnetic energy per unit volume stored in a solenoid in terms of magnetic field is . . . . . . .

If a current of $4$ $A$ produces a magnetic flux of $3 \times 10^{-3}$ $Wb$ through a coil of $400$ turns, the energy stored in the coil will be: (in $J$)

$A$ 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 ............ $J$.