# Magnetic Properties Of Material – Short Questions With Answer | Physics Class 12

## Very Important Questions Collection HSEB | Science Faculty Magnetic Properties Of Material – Physics Grade XII Short Questions with Answer (Solution)

1. Distinction between Ferromagnetic, Paramagnetic and Diamagnetic substance substances.
Ans. Difference between Ferromagnetic , paramagnetic and Diamagnetic substances are given in below table.

 Properties Ferromagnetic substance Paramagnetic substance Diamagnetic substance State They are solid They may be solid, liquid or gas. They may be solid, liquid and gas. Effect of magnet Strongly attracted by a magnet. Feebly attracted by a magnet. Feebly repelled by a magnet. Behaviour of non-uniform field Movement from low high field region. Movement from low to high field region. Movement from high to low field region. Behaviour in external magnetic field (Lines of induction) The density of lines of induction in the material is larger than the density of the lines of magnetic intensity. The density of the lines of induction in a little greater than that of the lines of magnetic intensity. The density of the lines of induction is little less than that of the lines of magnetic intensity. Effects of temperature Above curie point, a ferromagnetic substance become paramagnetic. With the rise of temperature a paramagnetic substance becomes a diamagnetic. No effect on a diamagnetic substance. Permeability Very high A little greater than unit. A little less than unit. Susceptibility Very high and positive. A little greater than unity and positive. A little less than unity and negative.

2. What is the source of magnetic properties of material?
Ans. Magnetism is an effect of electric charge in motion. The magnetic properties of material due to the atomic magnets, which are tiny circulating current in the form of electrons revolving in atomic orbit.

3. Explain Curie law of magnetism.
Ans. The Curie law deals about variation of intensity of magnetization with temperature. According to Curie law, the induction (B) and inversely proportional to the temperature (T).

4. Why is hammering demagnetize a magnet? Explain. OR What happens if a bar is dropped on a floor?
Ans. According to molecular theory of magnetism, each molecule of magnetic substance is a tiny magnet. In unmagnetized state, these small molecular magnets all oriented at random direction. After magnetization, they align along certain direction and form magnet. When magnet is hammered, the kinetic energy of molecules increase and the molecular arrangement get perturb and magnet losses its magnetic behavior. Hence, hammering of a magnet gets demagnetize.

5. What is magnetic domain?
Ans. The atom of a ferromagnetic materials possesses non zero magnetic moment. According to atomic view of magnetism, an atom acts as small magnet due to the orbital and spinning motion of its electrons. In small regions there are large numbers of atoms. These small regions in which all-atomic magnets align along same direction.These small regions of very strong magnetism inside the ferromagnetic material are called magnetic domain. There are very large number of domains, which are aligning along various directions.Hence, net magnetic moment is zero.

6. What is hysteresis ?
Ans. When a ferromagnetic substance is subjected to magnetizing field whose intensity vector H gradually increase from zero, the corresponding magnetic induction vector B is as shown in figure. The magnetic induction (vector B) lags behind magnetic field (vector H) in B.H.curve. This phenomenon of lagging of magnetic field behind magnetic induction is called hysteresis. The area enclosed by hysteresis curve measure the energy loss magnetization.

7. Name of the material used to make: Electromagnet, Permanent magnet, Transfer core, Moving coil galvanometer.
Ans. The material used to make :

1. Electromagnet => soft iron
2. Permanent core => steel
3. Transformer core => soft iron
4. Moving coil galvanometer => soft iron.

8. A bar magnet of iron is heated to 1000°C. Does it retain its magnetism on cooling ?
Ans. The Curie temperature of iron is 750°C, and above this temperature, iron loses its ferromagnetic and turn paramagnetic material. When it is cooled down, it cannot retain its magnetism itself as the atomic moment align randomly.

9. Why do we prefer soft iron for the core of transformer ?
Ans. The soft iron has small area of hysteresis loop with smaller retentivity but larger coercivity. As the core of a transformer goes through many alternate cycles of magnetization per second, lesser energy is lost due to small loop area and high magnetic is produced in it due to high retentivity that required for a transformer.

10. It is easier to demagnetize soft iron than steel. Explain.
Ans. The area under hysteresis curve for soft iron is small where as the area under hysteresis curve for steel is large.Larger the area under hysteresis curve more difficult to demagnetize. so due to small area under hysteresis curve for soft iron, it is easier to demagnetize it.

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### One Comment

1. clara
Posted September 6, 2016 at 7:48 pm

its is a really very helpful

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