If the current flowing through a coil is reduced by $50 \%$,then the energy stored in the coil will

$A$ coil with resistance $20\, \Omega$ and inductance $5\, H$ is connected to a $100\, V$ battery. The energy stored in the coil will be .... $J$.

$A$ current of $2\,A$ is increasing at a rate of $4\,A/s$ through a coil of inductance $2\,H$. The energy stored in the inductor per unit time is ... $J/s$.

If a current flowing in a coil is reduced to half of its initial value,the relation between the new energy $(E_2)$ and the original energy $(E_1)$ stored in the coil will be

Two circuits $A$ and $B$ are connected to identical d.c. sources each of e.m.f. $10 \ V$. Self-inductances of circuits $A$ and $B$ are respectively $L_A = 10 \ H$ and $L_B = 10 \ mH$. The total resistance of each circuit is $40 \ \Omega$. The ratio of energy consumed in circuit $A$ and circuit $B$ to build up the current to steady value is

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