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Characteristics of magnetic materials
Classification:
Materials with ferromagnetic properties have the following characteristics:
① Even if there is no external magnetic field, there are still magnetic moments in various small regions (magnetic domains) inside the material. However, in the absence of an external magnetic field, the direction of the magnetic moment of each magnetic domain is arbitrarily distributed, and the vector sum is zero, so the material as a whole is non-magnetic.
② Easy to magnetize. This is because the direction of the magnetic moment of each magnetic domain tends to shift to the direction of the magnetic field under the action of an external magnetic field, so that a large magnetic induction intensity B can be obtained. According to the formula B = μrB0(B0 is the magnetic induction intensity in vacuum), the relative permeability μr of the magnetic material is very large. In fact, the μr of the magnetic material reaches 10~10, while the μr of the non-magnetic material is 1.
③ There is a magnetic saturation phenomenon, that is, B increases with the increase of H, but after increasing to a certain value Bs, it will no longer increase with H. BS is the saturation magnetic induction of the magnetic material. The reason for the saturation phenomenon is that the magnetic moments of all magnetic domains are transferred to the magnetic field direction after H reaches a certain value. For this reason, B and H are not linearly related, so the magnetic permeability is not constant, but related to the magnetic field strength.
④ There is hysteresis. That is, the change of the magnetic induction intensity lags behind the change of the magnetic field.
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