A thin semicircular conducting ring (PQR) of radius $r$ is falling with its plane vertical in a horizontal magnetic field $B.$ The potential difference developed across the ring when its speed is $v,$ is

A conducting square frame of side $a$ and a long straight wire carrying current $I$ are located in the same plane as shown in the figure. The frame moves to the right with a constant velocity $V.$ The emf induced in the frame will be proportional to

A thin diamagnetic rod is placed vertically between the poles of an electromagnet. When the current in the electromagnet is switched on, then the diamagnetic rod is pushed up, out of the horizontal magnetic field. Hence the rod gains gravitational potential energy. The work required to do this comes from

A 800 turn coil of effective area $0.05$ m$^2$ is kept perpendicular to a magnetic field $5 \times 10^{-5}$ T$.$ When the plane of the coil is rotated by $90^\circ$ around any of its coplanar axis in $0.1$ s, the emf induced in the coil will be:

In which of the following devices, the eddy current effect is not used?

Two conducting circular loops of radii $R_1$ and $R_2$ are placed in the same plane with their centres coinciding. If $R_1 >> R_2,$ the mutual inductance $M$ between them will be directly proportional to:

A big circular coil of 1000 turns and average radius $10m$ is rotating about its horizontal diameter at $2 rad/s.$ If the vertical component of Earth’s magnetic field at that place is $2 \times 10^{-5} T$ and electrical resistance of the coil is $12.56 \Omega,$ then the maximum induced current in the coil will be:

The magnetic energy stored in an inductor of inductance $4 \mu H$ carrying a current of 2 A is:

In the above diagram, a strong bar magnet is moving towards solenoid-2 from solenoid-1. The direction of induced current in solenoid-1 and that in solenoid-2, respectively, are through the directions: