electromagnetic induction Questions

A coil having $n$ turns and resistance $4R\Omega$ is connected in a circuit with a resistor $R\Omega$. This combination is moved in time $t$ seconds from a magnetic flux $W_1$ weber to $W_2$ weber. The induced current in the circuit is:

In a uniform magnetic field of induction $B$, a wire in the form of a semicircle of radius $r$ rotates about the diameter of the circle with angular frequency $\omega$. The axis of rotation is perpendicular to the field. If the total resistance of the circuit is $R$, the mean power generated per period of rotation is:

A metal conductor of length $1\text{m}$ rotates vertically about one of its ends at angular velocity $5\text{radians per second}$. If the horizontal component of earth’s magnetic field is $0.2\times 10^{-4}\text{T}$, then the e.m.f. developed between the two ends of the conductor is: