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| Ferromagnetic Substances |
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Those substances which when placed in a magnetic field are strongly magnetized in the direction of the applied field are called ferromagnetic substance. E.g iron, nickel, cobalt etc. |
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Since the strong induced magnetic field is in the direction of the applied field, the resultant magnetic field inside the ferromagnetic material is very large; often thousand times greater than the magnetizing field. Hence the magnetic susceptibility is very large; often thousand times greater than the magnetizing field. Hence, the magnetic susceptibility of a ferromagnetic material is positive having a very high value, e.g. about 8000 for soft iron. |
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It is clear that relative permeability µr for such substances will be very high of the order of several thousands. It is clear that a substance whose relative permeability is very high is a ferromagnetic substance. It may be noted that in some ferromagnetic substances, the magnetism persists even when the external magnetic field is removed.
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Some properties of ferromagnetic substances are : |
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A ferromagnetic substance is strongly attracted by a magnet.
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When a rod of ferromagnetic substance is suspended freely in a uniform magnetic field, it quickly aligns itself in the direction of the applied field.
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When a ferromagnetic substance is placed in a non-uniform magnetic field, it movers from weaker to stronger regions of magnetic field.
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When a ferromagnetic substance is placed in a magnetic field, it is strongly magnetized in the direction of the applied field.
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When a ferromagnetic substance is placed in a magnetic field, the magnetic field lines tend to crowd into the substance.
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The magnetic susceptibility of a ferromagnetic substance is positive having a very high value.
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The relative permeability ( µr ) of a ferromagnetic substance is very high.
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