A ferromagnetic material is placed in an external magnetic field. The magnetic domains:

1.	must increase in size.
2.	must decrease in size.
3.	may increase or decrease in size.
4.	disappear.

If a magnetic dipole of dipole moment $\mu$ is rotated through an angle $\theta$ with respect to the direction of the magnetic field B, then work done is :

1. $\mu$Bsin$\theta$

2. $\mu$B(1-sin$\theta$)

3. $\mu$Bcos$\theta$

4. $\mu$B(1-cos$\theta$)

Magnetic permeability is maximum for

1. Diamagnetic substance

2. Paramagnetic substance

3. Ferromagnetic substance

4. Same for all three substances

The magnetic moment of a bar magnet shown in figure(i) is M.

If a hole is drilled through the magnet as shown in figure(ii), then the new magnetic moment of the magnet will be :

1. Equal to M

2. Less than M

3. More than M

4. Zero

When a substance is kept in a magnetic field, it gets repelled. Which of the following represents its susceptibility?

1. -0.0004

2. 0.0004

3. 1.000

4. -1.000

Magnetic susceptibility of a substance at \(27^{\circ}~\mathrm{C}\) is \(-0.00025\). Its magnetic susceptibility at \(127^{\circ}~\mathrm{C}\) is:
1. \(-0.000125\)
2. \(-0.0005\)
3. \(-0.00025\)
4. \(-0.00001\)

Magnetic induction at an axial point of a short magnet at a distance \(r\) from the centre of dipole is \(\vec B\). Its value at the equatorial point of the short magnet at the same distance from the centre of dipole is:

Consider a magnetic dipole kept in the east-west direction. Let P₁, P₂, Q₁, Q₂ be four points at the same distance from the dipole towards north, south, east and west of the dipole respectively. The directions of the magnetic field due to the dipole are the same only at:
1. P₁ and Q₁
2. P₂ and Q₁
3. P₁ and Q₂
4. Q₁ and Q₂

The magnetic moment of a bar magnet of length \(L\) and area of cross-section \(A\) is \(M\). If the magnet is cut into four identical parts each of length \(L\) and area of cross-section \(\frac{A}{4}\), then magnetic moment of each part is:

When a magnetic material is subjected to a very small magnetising force \(H,\) the intensity of magnetisation is proportional to: