What is the dimensional formula of magnetic flux?
1.
2.
3.
4.
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 e.m.f. 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:
1. | a | 2. | b |
3. | c | 4. | d |
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:
1. | parallel to the motion of wire. |
2. | along with XY. |
3. | perpendicular outside the paper. |
4. | perpendicular inside the paper. |
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.
2.
3.
4.
An inductor is connected to a direct voltage source through a switch. Then:
1. | a very large emf is induced in inductor when the switch is closed. |
2. | a large emf is induced when the switch is opened. |
3. | a large emf is induced whether the switch is closed or opened. |
4. | no emf is induced whether the switch is closed or opened. |
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.
2. 2L
3. 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