Two coils P and Q are kept near each other. When no current flows through coil P and current increases in coil Q at the rate $10 \mathrm{~A} / \mathrm{s}$, the emf in coil P is 12 mV . When coil Q carries no current and current of 1.5 A flows through coil P , the magnetic flux linked with the coil Q in mWb is

When magnetic flux changes from $6.5 \times 10^{-2} \mathrm{~Wb}$ to $11 \times 10^{-2} \mathrm{~Wb}$ and the change in current is 0.03 A , the coefficient of mutual inductance will be

Two circuits A and B are connected to identical d.c. sources each of e.m.f. 10 volt. Self-inductances of circuits A and B are respectively $\mathrm{L}_{\mathrm{A}}=10 \mathrm{H}$ and $\mathrm{L}_{\mathrm{B}}=10 \mathrm{mH}$. 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

A magnetic field $4 \times 10^{-2} \mathrm{~T}$ acts at right angles to a coil of area $100 \mathrm{~cm}^2$ with 50 turns. The average e.m.f. induced in the coil is 0.1 V , when it is removed from the field in time ' $t$ '. The value of ' $t$ ' is