Although magnets are used in many places in our lives, many products will shield the magnetic field of magnets to a certain extent. Shielding the magnetic field does not mean demagnetization, but to avoid too strong magnetic field affecting the operation of other parts or focusing the magnetic field. So today, I will make a share about principle, material and some application.
The materials we commonly use for shielding strong magnets are: iron sheet, steel plate, cast iron, paramagnetic materials, iron powder cloth, non-magnetic magnets and other soft magnetic materials.
Magnetic field shielding principle:
The shield provides a low magnetoresistive magnetic circuit for the interference magnetic field, so as to shunt the interference magnetic field. Therefore, the selection of high permeability materials such as steel, iron and pomo and the design of closed boxes are the two key factors of magnetic shielding. The principle of magnetic shielding is that the far field of the radiation interference source is shielded by a metal shield through the reflection and absorption of electromagnetic waves, that is, the electric field and magnetic field components generated by the field source are shielded at the same time. As the frequency increases, the wavelength becomes equal to the size of the aperture on the shield, resulting in the aperture leakage of the shield becoming the most critical control factor of electromagnetic shielding.
Magnetic shielding packing box
In short, Magnetic field has N poles and S poles, and N and S are connected to a magnetic field line with a loop that cannot be seen with the naked eye. When we shield the magnetic field, we use ferromagnetic materials to reflect the magnetic field line back and make it produce a loop in the shortest route, so as to achieve the effect of shielding part of the magnetic field line and reduce the effect of magnetic field line in the space outside the shield. It has achieved the effect of isolating the magnetic effect of strong magnets.
A specific example: the movement in the manipulator watch is made of steel. If the watch is placed near a magnet, the steel movement will be magnetized. Especially when the spring is magnetized, the table will stop immediately. Therefore, the watch needs to be covered with a material that can defend against magnetic force and make the magnetic field impenetrable. Interestingly, the material that can cover the external magnetic field turns out to be the easily magnetized iron itself. To prove this, you can put a small compass inside an iron ring, and you can see that the small magnetic needle will not be attracted to the magnet outside the ring. So, if you have a watch with an iron or steel shell, you can protect the steel parts in the watch from the magnetic force. Even if the watch is placed near a strong magnetic field, its accuracy will not be reduced at all. As for the gold and silver watches made of gold or silver shells, although they are very valuable, they must not be placed near the magnet, because it is not anti-magnetic. It can be seen that the iron wrapper can cover the outside magnetic field, so that the inside is not affected by the external magnetic field, and the iron products placed in it will not be magnetized. This phenomenon is called magnetic shielding in physics.
The practical application of magnetic insulation: The shielding of strong magnet magnetism is widely used in our daily life. For example: motor motor shell, electric meter shell, electric cabinet, speaker speaker, etc.. 0 distance shielding and space distance shielding, 0 distance shielding is the most commonly used, such as the motor belongs to 0 distance shielding, when the current through the coil after the magnetic field generated in the motor housing under the action of the magnetic field line will not leak.
The above is about the principle of magnetic shielding and the answer of commonly used materials, I hope to help you! In the process of transporting magnets, we will also use shielding materials for "demagnetization" (actually magnetic insulation) according to demand. If you have any questions or magnet needs, please contact us!
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