Two coils having self-inductance $L_1 = 75$ mH and $L_2 = 48$ mH are coupled with each other. If the mutual inductance of the coils is 37.2 mH, then coefficient of coupling will be

A straight line conductor of length 0.4 m is moved with a speed of $7.0 \text{ ms}^{-1}$ perpendicular to magnetic field of intensity $0.8 \text{ Wb m}^{-2}$. The induced e.m.f. across the conductor is

Three coils of inductance, $L_1$ = 2 H, $L_2$ = 3 H and $L_3$ = 6 H are connected so that they are separated from each other. To obtain the effective inductance of $\dfrac{18}{11}$ H between points A and B, out of the following figures, the correct one is

Two coils have self inductance $L_1$ and $L_2$. The current through them is increasing at constant rate. If the power dissipated in both the coils is same, then the ratio of energy stored in the coil having inductance $L_1$ to that in $L_2$ is