$A$ metal disc rotates freely between the poles of a magnet in the direction indicated. Brushes $P$ and $Q$ make contact with the center (axle) and the edge of the disc,respectively. What current,if any,flows through $R$?

At a place,the value of the horizontal component of the Earth's magnetic field $H$ is $3 \times 10^{-5} \, Wb/m^2$. $A$ metallic rod $AB$ of length $2 \, m$,placed in the east-west direction with end $A$ towards the east,falls vertically downward with a constant velocity of $50 \, m/s$. Which end of the rod becomes positively charged,and what is the value of the induced potential difference between the two ends?

$A$ rectangular loop $PQRS$ is being pulled with a constant speed into a uniform transverse magnetic field by a force $F$ (as shown). The $e.m.f.$ induced in side $PS$ and the potential difference between points $P$ and $S$ respectively are (Resistance of the loop $= r$)

$A$ certain elastic conducting material is stretched into a circular loop. It is placed with its plane perpendicular to a uniform magnetic field $B = 0.8 \, T$. When released,the radius of the loop starts shrinking at a constant rate of $dr/dt = -2 \, cm/s$. The induced emf in the loop at an instant when the radius of the loop is $r = 10 \, cm$ will be $........ mV$.

$A$ conducting circular loop is placed in the $X-Y$ plane in the presence of a magnetic field $\overrightarrow{B} = (3t^3 \hat{j} + 3t^2 \hat{k})$ in $SI$ units. If the radius of the loop is $1 \ m$,the induced emf in the loop at time $t = 2 \ s$ is $n\pi \ V$. The value of $n$ is:

$A$ circular coil of radius $10 \, cm$ and resistance of $2 \, \Omega$ is placed with its plane perpendicular to the horizontal component of the earth's magnetic field. It is rotated about its vertical diameter through $180^{\circ}$ in $0.25 \, s$. If the magnitude of the induced emf is $3.8 \times 10^{-3} \, V$, then the number of turns of the coil is (Horizontal component of earth's magnetic field at the place is $3 \times 10^{-5} \, T$) (in $turns$)