$A$ metallic rod of length $l$ is tied to a string of length $2l$ and made to rotate with angular speed $\omega$ on a horizontal table with one end of the string fixed. If there is a vertical magnetic field $B$ in the region,the $e.m.f.$ induced across the ends of the rod is

$A$ horizontal straight wire $10 \; m$ long extending from east to west is falling with a speed of $5.0 \; m \, s^{-1}$,at right angles to the horizontal component of the earth's magnetic field,$0.30 \times 10^{-4} \; Wb \, m^{-2}$.
$(a)$ What is the instantaneous value of the $emf$ induced in the wire?
$(b)$ What is the direction of the $emf$?
$(c)$ Which end of the wire is at the higher electrical potential?

The figure shows a square loop of side $5 \, cm$ being moved towards the right at a constant speed of $1 \, cm/s$. The front edge enters the $20 \, cm$ wide magnetic field at $t = 0$. Find the magnitude of the $emf$ induced in the loop at $(a) \, t = 2 \, s$, $(b) \, t = 10 \, s$, and $(c) \, t = 22 \, s$.

$A$ rectangular coil $ABCD$ is rotated anticlockwise with a uniform angular velocity about the axis shown in the diagram below. The axis of rotation of the coil as well as the magnetic field $B$ are horizontal. The induced $e.m.f.$ in the coil would be maximum when

$A$ conducting rod of length $l$ moves with a constant velocity $\upsilon$ perpendicular to a long,straight wire carrying a current $I$,as shown in the figure. Calculate the $emf$ generated between the ends of the rod.

When a rod of length $l$ is rotated with angular velocity $\omega$ in a uniform magnetic field of induction $B$ perpendicular to the plane of rotation,about one of its ends,the induced emf across its ends is: