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SEM-3RD�SUB-EEM�PREPAIRED BY-SUMAN SAHU,ASST. H.O.D. ELECTRICAL ENGINEERING� CHAPTER 5:MAGNETIC MATERIAL

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  • Introduction
  • Terms connected with magnetic materials
  • Classification with Properties
  • Hysteresis
  • Applications

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  • Magnetic Materials are those materials in which a state of magnetization can be induced.

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  • Such materials when magnetized create a magnetic field in the surrounding space.

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  • Magnetic force
  • Magnetic flux density
  • Magnetic field strength
  • Relative permeability
  • Absolute permeability
  • Remanance
  • Retentivity
  • Curie temperature (Tc)
  • Hysteresis loop & losses

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  • Ferromagnetic
  • Paramagnetic
  • Diamagnetic
  • Magnetically Soft material
  • Magnetically Hard material

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  • A type of material that is highly attracted to magnets and can become permanently magnetized is called as ferromagnetic.

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  • The relative permeability is much greater than unity and are dependent on the field strength.

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  • These have high susceptibility.

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  • Fe, Co, Ni, Cr, Mn are such materials.

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  • It is a substance or body which very weakly attracted by the poles of a magnet, but not retaining any permanent magnetism.

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  • These have relative permeability slightly greater than unity and are magnetized slightly.

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  • They attract the lines of forces weakly.

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are such materials.

  • Al, Pt, Ca, O2

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  • It is a substance which create a magnetic field in opposite to an externally applied field.

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  • Susceptibility is negative.

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  • These have relative permeability slightly less than unity.

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  • They reppel the lines of force slightly.

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  • The examples are bismuth silver, copper and hydrogen.

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  • Characteristics :
    1. They have high permeability.
    2. The magnetic energy stored is not high.
    3. They have negligible coercive force.
    4. They have low remanence.
    5. Hysteresis loop is narrow.

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  • Examples :

pure or ingot iron, cast iron, carbon steel,

manganese & nickel steel, etc.

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  • Characteristics :
    1. They possess high value of BH product.
    2. High retentivity.
    3. High coercivity.
    4. Strong magnetic reluctance.
    5. Hysteresis loop is more rectangular in

shape.

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  • Examples :

Tungsten steel, cobalt steel, chromium steel, etc.

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  • Ferromagnetic materials are used in magnetic recording devices, such as for cassette tapes, floppy discs for computers, and the magnetic stripe on the back of credit cards.

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  • Diamagnetic materials are used for magnetic levitation, where an object will be made to float in are above a strong magnet.

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  • Magnetic soft materials are used in making electromagnets and these electromagnets are used in telephone receiver, bells, loud speakers etc.

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  • Magnetic hard materials are used in making permanent magnets.

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