21
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Which materials are called as non – magnetic material?
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Non – magnetic materials
- The materials which do not
exhibit property of magnetic are called as non – magnetic materials.
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22
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What do you mean by the para magnetic material,
dia magnetic material and ferromagnetic material?
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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.
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23
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Describe the different types of ferromagnetic
material.
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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.
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24
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What do you mean by Ferrites?
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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.
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25
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Describe the properties of Soft ferrites.
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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
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26
|
Which parameters affect the magnetic property of the
material?
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- 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.
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27
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State the Weber’s Molecule theory of magnetism.
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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.
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28
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Give reason : The magnetism of magnetic material
reduces due to heating.
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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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