In what form is the energy stored in an inductor?

The energy stored in a coil of inductance $L$ carrying a steady current $i$ is in the form:

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

Energy in a current carrying coil is stored in the form of

Define an inductor. Derive the equation for the energy $U = \frac{1}{2}LI^2$ stored in an inductor.

$A$ coil of self-inductance $0.5 \ mH$ carries a current of $2 \ A$. The energy stored in Joule is . . . . . . .