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.

Magnetic permeability is maximum for

1. Diamagnetic substance

2. Paramagnetic substance

3. Ferromagnetic substance

4. Same for all three substances

The area enclosed by hysteresis loop is a measure of :

1. Permeability

2. Susceptibility

3. Retentivity

4. Energy loss per cycle

Line joining places of zero angle of dip on earth surface is called :

1. Isoclinic line

2. Aclinic line

3. Isogonic line

4. Agonic line

When a dip circle is kept at a place, the angle of dip obtained is 45$°$. When the dip circle is rotated about its vertical axis by 90$°$, the angle of dip obtained is 60$°$. The true dip at that place is :

1. cot^-1 $\left(\frac{2}{\sqrt{3}}\right)$

2. cot^-1$\left(\frac{4}{3}\right)$

3. ${\tan }^{-1}\left(\frac{2}{\sqrt{3}}\right)$

4. ${\tan }^{-1}\left(\frac{4}{3}\right)$

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

The time period of vibration of a bar-magnet in a vibration magnetometer is \(T\). If the magnet is cut into \(n\) identical parts such that the length of each part is equal to the length of the original magnet, then the time period of vibration of one part in the vibration magnetometer is:
1. \(\frac{T}{n}\)
2. \(nT\)
3. \(n^2T\)
4. \(T\)

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. \(-0.00001\)