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 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

The figure illustrates how B, the flux density, inside a sample of unmagnetized ferromagnetic material varies with B₀, the magnetic flux density, in which the sample is kept. For the sample to be suitable for making a permanent magnet:

1. OQ should be large and OR should be small

2. OQ and OR should both be large

3. OQ should be small and OR should be large

4. OQ and OR should both be small

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.

The magnetic susceptibility χ of a ferromagnetic material varies with temperature, as:

1.		2.
3.		4.

If A is the area of the graph of the intensity of magnetisation in ferromagnetic material versus magnetising field intensity, V is the volume of the magnetic sample and n is the frequency of alternating magnetic field, then the rate of hysteresis loss in the substance is 

1. A

2. AVn

3. $\frac{AV}{n}$

4. $\frac{A}{nV}$

The area enclosed by hysteresis loop is a measure of :

1. Permeability

2. Susceptibility

3. Retentivity

4. Energy loss per cycle