15/03/2020

Magnetic Hysteresis Interview Question Answer - 2


21
Which materials are called as non – magnetic material?


Non – magnetic materials
  • The materials which do not exhibit property of magnetic are called as non – magnetic materials.


22
What do you mean by the para magnetic material, dia magnetic material and ferromagnetic material?


Paramagnetic material
  • They are materials whose relative permeability slightly greater than unity.
  • These materials not attracted by magnets. E.g. Aluminum, air, platinum etc.

Dia magnetic material
  • They are materials whose relative permeability less than unity.
  • These materials are repelled by magnet. E.g. Copper, zinc, lead, bismuth etc

Ferromagnetic material
  • They are materials whose relative permeability much greater than unity.
  • These materials are strongly attracted by magnet.
  • It has high permeability. 
  • The para magnetic and dia magnetic are in the category of non – magnetic material.


23
Describe the different types of ferromagnetic material.


Soft ferromagnetic material
  • They are material in which magnetize and demagnetize done very easily.
  • Therefore they have small hysteresis loop, low coercive force and high relative permeability.
  • They are suitable for application of electromagnets, electrical motors, generators, transformers relays etc due to easy magnetization and demagnetization.

Hard ferromagnetic material
  • It is very difficult to magnetize and demagnetize hard ferro – magnetic materials.
  • They have low permeability and high coercive force.
  • They are suitable for making permanent magnets therefore they are also called as permanent magnet material. They have high hysteresis loss.


24
What do you mean by Ferrites?


Ferrites
  • They have intermediate position between ferromagnetic and non – magnetic materials.
  • The normal operating frequency of ferrite is 20 kHz.
  • They have high electrical resistivity almost 107 times greater than that of silicon steel.
  • There are two types of ferrites.

( a ) Soft ferrites
  • They have square hysteresis loop and provides high resistance to demagnetization.
  • The soft ferrites are used for high frequency applications.

( b ) Hard ferrites
  • They have hexagonal structure.
  • They are easy to magnetize. 
  •  They are used in generators, relays and magnets of loud speakers, receivers etc.


25
Describe the properties of Soft ferrites.


Properties of soft ferrites
  • High electrical resistivity
  • Good magnetic property particular at high frequency
  • Superior corrosion resistance
  • Low curie point
  • Inferior mechanical property
  • Low saturation magnetic flux density


26
Which parameters affect the magnetic property of the material?


  • The magnetic property of the material depends upon the spin movement of the electrons of the atom in the material.
  • Half of the electrons in the non – magnetic material spin in the clockwise direction whereas the half of the electrons in the anti-clockwise direction. 
  • This will result net field cancel out therefore the material do not exhibit any magnetic property.
  • More number of electrons spin in the one direction than that of other direction in the magnetic material. 
  • This will result net magnetic field is produced therefore each atom of the material becomes small magnet.


27
State the Weber’s Molecule theory of magnetism.


Weber’s Molecule theory of magnetism
  • This theory is related to molecule alignment of the magnetic material.
  • All the magnetic substances are composed to tiny molecule magnets.
  • All the magnet material has most of its molecular magnets arrange such that north poles of each molecule aligns in one direction whereas the south pole of each molecule aligns in opposite direction.
  • When all the molecule magnets are fully aligned, it is called as saturated magnetism
  • All the molecule magnets in the un – magnetized substances are randomly oriented.


28
Give reason : The magnetism of magnetic material reduces due to heating.


Effect of heating on magnetism
  • When the magnetic material is magnetized, some of the molecule magnets get kinetic energy whereas some may back in the closed chain arrangement. 
  • The magnetism reduces slightly due to this reason.




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