Two identical induction coils,each of inductance $L$,are joined in series and placed very close to each other such that the winding direction of one is exactly opposite to that of the other. What is the net inductance?

Two identical inductors, each of inductance $L$, are connected in two different configurations $P$ and $Q$, through which a time-varying current $I(t)$ flows. The induced emf between points $a$ and $b$ for configuration $P$ is $E_P$ and that for configuration $Q$ is $E_Q$. The ratio $E_P/E_Q$ is: [Neglect the effect of mutual inductance.]

In the given circuit, the current through the $5 \, mH$ inductor in steady state is

$A$ coil of inductance $L$ is divided into four equal parts and all the parts are connected in parallel. The effective inductance of the combination is

Two inductors,each of inductance $L$,are connected in parallel. One more inductor of value $5 \text{ mH}$ is connected in series with this configuration,and the effective inductance is $15 \text{ mH}$. The value of $L$ is . . . . . . $\text{mH}$.

The inductance between $A$ and $D$ is