A current carrying coil is placed with its axis perpendicular to N-S direction. Let horizontal component of earth's magnetic field be ${\mathrm{H}}_0$ and magnetic field inside the loop be H. If a magnet is suspended inside the loop, it makes angle $\mathrm{\theta }$ with H. Then $\mathrm{\theta \; equal\; to:}$

1. ${\tan }^{-1}\left(\frac{H_0}{H}\right)$

2. ${\tan }^{-1}\left(\frac{H}{H_{\mathit{0}}}\right)$

3. $\cos e{c}^{-1}\left(\frac{H}{H_{\mathit{0}}}\right)$

4. $co{t}^{-1}\left(\frac{H_0}{H}\right)$

The vertical component of the earth's magnetic field is zero at:

1. The magnetic poles.

2. The magnetic equator.

3. The geographic poles.

4. The geographic equator.

The relation amongst the three elements of Earth's magnetic field, namely horizontal component H, vertical component V and dip angle$$ $\delta$ is: ($B_E$=total magnetic field):

1. V=$B_E$tan$\delta$, H=$B_E$

2. V=$B_E$sin$\delta$, H=$B_E$cos$\delta$

3. V=$B_E$cos$\delta$, H=$B_E$sin $\delta$

4. V=$B_E$, H=$B_E$tan$\delta$ 

A dip needle vibrates in the vertical plane perpendicular to the magnetic meridian. The time period of vibration is found to be 2 seconds. If the same needle is then allowed to vibrate in the horizontal plane and the time period is again found to be 2 seconds, then the angle of dip is:

1. 0^o

2. 30^o

3. 45^o

4. 90^o

A dip needle in a plane perpendicular to magnetic meridian will remain:
1. Vertical
2. Horizontal
3. In any direction
4. At an angle of dip to the horizontal

The earth's magnetic field at a certain place has a horizontal component 0.3 Gauss and the total strength 0.5 Gauss. The angle of dip is:

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

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

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

4. ${\sin }^{-1}\left(\frac{3}{5}\right)$

The current of 30 A is flowing in a vertical straight wire. If the horizontal component of the earth's magnetic field is 2 x 10^-5 Tesla, then the position of the null point will be:

1. 0.9 m 

2. 0.3 mm

3. 0.3 cm 

4. 0.3 m

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

Above Curie temperature:

1. a ferromagnetic substance becomes paramagnetic.

2. a paramagnetic substance becomes diamagnetic.

3. a diamagnetic substance becomes paramagnetic.

4. a paramagnetic substance becomes ferromagnetic.