Each atom of an iron bar$$ (5 cm × 1 cm × 1 cm) has a magnetic moment $1.8\times {10}^{-23} A{m}^2$. Knowing that the density of iron is $7.78\times {10}^3 kg{m}^{-3}$ atomic weight is 56 and Avogadro's  number is $6.02\times {10}^{23}$the magnetic moment of the bar in the state of magnetic saturation will be:

1. 4.75 Am²                 

2. 5.74 Am²

3. 7.54 Am²                 

4. 75.4 Am²

A dip needle vibrates in the vertical plane perpendicular to the magnetic meridian. The time period of vibration is found to be 2 seconds. 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 lies initially in the magnetic meridian when it shows an angle of dip $\theta$ at a place. The dip circle is rotated through an angle x in the horizontal plane and then it shows an angle of dip $\theta \text{'}$. Then $\frac{\tan \theta \text{'}}{\tan \theta }$ is

1. 1/cos x

2. 1/sin x

3. 1/tan x

4. cos x

A bar magnet has coercivity $4\times {10}^3 A{m}^{-1}$. It is desired to demagnetize it by inserting it inside a solenoid 12 cm long and having 60 turns. The current that should be sent through the solenoid is

1. 2 A                            2. 4 A

3. 6 A                            4. 8 A

For substances hysteresis (B - H) curves are given as shown in figure. For making temporary magnet which of the following is best?

1.		2.
3.		4.

The variation of magnetic susceptibility $\left(\chi \right)$ with temperature for a diamagnetic substance is best represented by

1. 

2. 

3. 

4. 

The variation of magnetic susceptibility $\left(\chi \right)$ with absolute temperature T for a ferromagnetic material is

1.                           2. 

3.                           4. 

The relative permeability $\left({\mu }_r\right)$ of a ferromagnetic substance varies with temperature (T) according to the curve:

1. A                              

2. B

3. C                              

4. D

Which curve may best represent the current deflection in a tangent galvanometer ?

(a) A                               (b) B

(c) C                               (d) D

Some equipotential surfaces of the magnetic scalar potential are shown in the figure. The magnetic field at a point in the region is: (X-axis read in cm)                                                                   

(1) ${10}^{-4} T$                        

(2) $2\times {10}^{-4} T$

(3) $0.5\times {10}^{-4} T$                

(4) None of these