Magnetism and Matter

At a point A on the earth’s surface the angle of dip, = +25 . At a point B on the earth's surface the angle of dip, = -25 . We can interpret that :

1. A is located in the southern hemisphere and B is located in the northern hemisphere.
2. A is located in the northern hemisphere and B is located in the southern hemisphere.
3. A and B are both located in the southern hemisphere.
4. A and B are both located in the northern hemisphere.

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

1. The current source
2. The magnetic field
3. The lattice structure of the material of the rod
4. The induced electric field due to the changing magnetic field

If 1 and 2 be the apparent angles of dip observed in two vertical planes at right angles to each other, then the true angle of dip is given by

1. 2 = 2 1 + 2 2
2. 2 = 2 1 - 2 2
3. 2 = 2 1 - 2 2
4. 2 = 2 1 + 2 2

The magnetic susceptibility is negative for

1. ferromagnetic material only
2. paramagnetic and ferromagnetic materials
3. diamagnetic material only
4. paramagnetic material only

A bar magnet is hung by a thin cotton thread in a uniform horizontal magnetic field and is in equilibrium state. The energy required to rotate it by 60 is W. Now the torque required to keep the magnet in this new position is

1. W 3
2. 3W
3. 3W2
4. 2W 3

Following figures show the arrangement of bar magnets in different configurations. Each magnet has magnetic dipole moment m. Which configuration has highest net magnetic dipole moment ? [figure]

1. (1)
2. (2)
3. (3)
4. (4)

A bar magnet of length 'l' and magnetic dipole moment 'M' is bent in the form of an arc as shown in figure. The new magnetic dipole moment will be [figure]

1. 2 M
2. M2
3. M
4. 3 M

A bar magnet of magnetic moment M is placed at right angles to a magnetic induction B. If a force F is experienced by each pole of the magnet, the length of the magnet will be

1. MB/F
2. BF/M
3. MF/B
4. F/MB

A magnetic needle suspended parallel to a magnetic field requires 3 J of work to turn it through 60 . The torque needed to maintain the needle in this position will be

1. 2 3 J
2. 3 J
3. 3 J
4. 32 J

A compass needle which is allowed to move in a horizontal plane is taken to a geomagnetic pole. It

1. will become rigid showing no movement
2. will stay in any position
3. will stay in north-south direction only
4. will stay in east-west direction only