The self inductance of an air-cored solenoid of length 40 cm , diameter 7 cm having 200 turns is nearly

A coil having 100 square loops each of side 10 cm is placed such that its plane is normal to a magnetic field, which is changing at a rate of $0.7 \mathrm{Ts}^{-1}$. The emf induced in the coil is

When current in a coil changes from 2 A to 5 A in time of 0.3 s , if the emf induced in the coil is 40 mv , then the self inductance of the coil is

A coil of resistance $200 \Omega$ is placed in a magnetic field. If the magnetic flux $\phi$ (in weber) linked with the coil varies with time ' $t$ ' (in second) as per the equation $\phi=50 t^2+4$, then the current induced in the coil at a time $t=2 \mathrm{~s}$ is