Magnetism and Matter · Question 2

An iron bar of length L has magnetic moment M. It is bent at the middle of its length such that the two arms make an angle 60 with each other. The magnetic moment of this new magnet is :

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

The magnetic potential energy, when a magnetic bar of magnetic moment m is placed perpendicular to the magnetic field B is

1. - mB2
2. Zero
3. -mB
4. mB

The incorrect relation for a diamagnetic material (all the symbols carry their usual meaning and is a small positive number) is

1. < 0
2. 0 r < 1
3. -1 < 0
4. 1 < r < 1 +

The magnetic moment and moment of inertia of a magnetic needle as shown are, respectively, 1.0 10-2 A m2 and 10-6 2 kg m2. If it completes 10 oscillations in 10 s, the magnitude of the magnetic field is [figure]

1. 0.4 T
2. 4 T
3. 0.4 mT
4. 4 mT

The magnetic moment of an iron bar is M. It is now bent in such a way that it forms an arc section of a circle subtending an angle of 60 at the centre. The magnetic moment of this arc section is

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

The net magnetic flux through any closed surface is :

1. Positive
2. Infinity
3. Negative
4. Zero

An iron rod of susceptibility 599 is subjected to a magnetizing field of 1200 A m-1. The permeability of the material of the rod is : ( 0 = 4 10-7 T m A-1)

1. 8.0 10-5 T m A-1
2. 2.4 10-5 T m A-1
3. 2.4 10-7 T m A-1
4. 2.4 10-4 T m A-1

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