A horizontal telephone wire $1 \mathrm{km}$ long is lying east-west in earth’s magnetic field. It falls freely to the ground from a height of $10 \mathrm{m}$. Calculate the emf induced in the wire on striking the ground. Given $B_H=0.32 \mathrm{G}$.

Figure shows a rectangular conducting loop $PQRS$ in which the arm $PQ$ is free to move. A uniform magnetic field acts in the direction perpendicular to the plane of the loop. Arm $PQ$ is moved with a velocity $v$ towards the arm $RS$. Assuming that the arms $QR$, $RS$ and $SP$ have negligible resistances and the moving arm $PQ$ has the resistance $R$, obtain the expression for the current in the loop

Figure shows a rectangular conducting loop $PQRS$ in which the arm $PQ$ is free to move. A uniform magnetic field acts in the direction perpendicular to the plane of the loop. Arm $PQ$ is moved with a velocity $v$ towards the arm $RS$. Assuming that the arms $QR$, $RS$ and $SP$ have negligible resistances and the moving arm $PQ$ has the resistance $R$, obtain the expression for the force.

Figure shows a rectangular conducting loop $PQRS$ in which the arm $PQ$ is free to move. A uniform magnetic field acts in the direction perpendicular to the plane of the loop. Arm $PQ$ is moved with a velocity $v$ towards the arm $RS$. Assuming that the arms $QR$, $RS$ and $SP$ have negligible resistances and the moving arm $PQ$ has the resistance $R$, obtain the expression for the power required to move the arm $PQ$.

A rectangular loop $PQMN$ with movable arm $PQ$ of length $10 \mathrm{cm}$ and resistance $2 \mathrm{\Omega }$ is placed in a uniform magnetic field of $0.1 \mathrm{T}$ acting perpendicular to the plane of the loop as is shown in the figure. The resistances of the arms $MN$, $NP$ and $MQ$ are negligible. Calculate the current induced in the loop when arm $PQ$ is moved with velocity $20 \mathrm{m} {\mathrm{s}}^{-1}$.