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. \(-0.00001\)

Locus of all points having the same dip on the magnetic map of the earth is known as :

1. Isodynamic line

2. Isogonic line

3. Isothermal line

4. Isoclinic line

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