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

When a current of 4 mA passes through an inductor, if the flux linked with it is $32 \times 10^{-6} \mathrm{Tm}^2$, then the energy stored in the inductor is

If a wheel with 24 metallic spokes each 40 cm long is rotated with a speed of $180 \mathrm{rev} / \mathrm{min}$ in a plane normal to the horizontal component of Earth's magnetic field, the emf induced between the axle and the rim of the wheel is $E$. If the number of spokes is made 12 and the wheel is rotated with a speed of $90 \mathrm{rev} / \mathrm{min}$ in the same field, the induced emf is