A cylindrical magnet is kept along the axis of a circular coil. On rotating the magnet about its axis, the coil will have induced in it:

1.	No current
2.	A current
3.	Only an e.m.f.
4.	Both an e.m.f. and a current

The magnetic flux through a coil varies with time \(t\) as shown in the diagram. Which graph best represents the variation of the emf \(E\) induced in the coil with time \(t\)?

1.		2.
3.		4.

A bar magnet is made to fall through a long surface copper tube. The speed (v) of the magnet as a function of time (t) is best represented by:

When a conducting wire XY is moved towards the right, a current flows in the anti-clockwise direction. Direction of magnetic field at point O is:

Eddy currents are induced when:

1. A metal block is kept in a changing magnetic field.

2. A metal block is kept in a uniform magnetic field.

3. A coil is kept in a uniform magnetic field.

4. Current is passed in a coil.

The magnetic energy stored in a long solenoid of an area of cross-section A in a small region of length L is:

1. $\frac{{\mathrm{B}}^2\mathrm{AL}}{2{{\mathrm{\mu }}_0}^2}$

2. $\frac{\mathrm{AL}}{2{\mathrm{\mu }}_0}$

3. $\frac{1}{2}{\mathrm{\mu }}_0{\mathrm{B}}^2\mathrm{AL}$

4. $\frac{{\mathrm{B}}^2\mathrm{AL}}{2{\mathrm{\mu }}_0}$

An inductor is connected to a direct voltage source through a switch. Then:

A long solenoid has self-inductance L. If its length is doubled keeping total number of turns constant, then its new self-inductance will be:

1. $\frac{\mathrm{L}}{2}$

2. 2L

3. L

4. $\frac{\mathrm{L}}{4}$

With the decrease of current in the primary coil from 2 A to zero in 0.01 s, the e.m.f. generated in the secondary coil is \(1000~\mathrm{V}\). The mutual inductance of the two coils is:

1. 1.25 H

2. 2.50 H

3. 5.00 H

4. 10.00 H

Two coaxial coils are very close to each other and their mutual inductance is 5 mH. If a current 50 sin 500t is passed in one of the coils, then the peak value of induced e.m.f. in the secondary coil will be: