The wing span of an aeroplane is $20$ $m$. It is flying in a field where the vertical component of the Earth's magnetic field is $5 \times 10^{-5} \, T$,with a velocity of $360 \, km/h$. The potential difference produced between the wing tips will be ....... $V$.

$A$ conducting wire is dropped along the east-west direction. Then,

$A$ wheel with $10$ spokes,each of length $L \ m$,is rotated with a uniform angular velocity $\omega$ in a plane normal to a magnetic field $B$. What is the emf induced between the axle and the rim of the wheel?

In the given figure,in which direction should the rod be moved to induce an $emf$ between its two ends?

$A$ rectangular loop is provided with a sliding connector of length $1 \, m$ and resistance $2 \, \Omega$. It is placed in a uniform magnetic field of $2 \, T$ perpendicular to the plane of the loop. The external force required to keep the connector moving with a uniform velocity of $2 \, ms^{-1}$ is: (in $N$)

Two conducting rings $P$ and $Q$ of radii $r$ and $2r$ rotate uniformly in opposite directions with centre of mass velocities $2v$ and $v$ respectively on a conducting surface $S$. There is a uniform magnetic field of magnitude $B$ perpendicular to the plane of the rings. The potential difference between the highest points of the two rings is