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Relationship between the size of magnet and its suction

time2021/08/30

The magnetic force of a magnet is often closely related to the raw material, performance, size and shape of the magnet. However, when the materials are the same, the properties are the same and the shape is the same, magnets of different sizes. What's the difference in suction?
Relationship between the size of magnet and its suction

1. Generation of magnetic field force


The essence of magnetism comes from the directional arrangement of magnetic domains. Because there are magnetic domains in magnetic materials, the electron spin of magnetic domains produces electric field force. When the magnetic domains are disordered, the electric field forces cancel each other, and when the magnetic domains are aligned, the magnetic field force is generated.


2. Three factors affecting the magnetic force of magnet


1)     Factors affecting magnet magnetic force - temperature

Due to dozens of magnet types (such as ferrite magnet, Nd-Fe-B magnet, bonded Nd-Fe-B, aluminum nickel cobalt, shirt cobalt, iron chromium cobalt, injection molded ferrite, etc.) and materials, there are corresponding temperature restrictions. Generally speaking. During the use of the product, there will be no demagnetization when the temperature is lower than the limit of the magnet.

2)     The second factor affecting the magnetic force of magnet: the existence of alternating magnetic field.

People who have a certain understanding of magnets know that magnets are divided into N, S poles or multipoles. If there is another magnetic field around the magnet, it will offset - part of the magnetic force of the magnet. It is also said that it will demagnetize within the range of service temperature.

3)     Three factors affecting the magnetic force of magnet: mechanical vibration

This is related to the assembly. The magnet rubs the product during the assembly process. Because the material characteristic of the magnet is fragile, the body is worn and the size becomes smaller. So the magnet will slowly weaken


3. When other conditions are the same, the influence of size on magnetic force


Generally, the larger the size, the greater the suction, but the growth of suction is affected by the shape of the product

Shape has a great influence, that is, the ratio of height to diameter. We take N40 brand of NdFeB magnet and axial magnetization as an example,

As shown in Figure 3 below, when the height of the magnet is fixed at 1mm, the diameter gradually increases from D1 to D10, and the suction increases accordingly

The rise is obvious and linear. Fig. 4

, the fixed diameter is D1, the magnet height increases from 1mm to 10mm, and the suction increases

The mode has changed. The suction increases greatly between 1mm and 3mm in height, but after 3mm,

Although the magnet volume has been increasing, the growth rate of suction has slowed down significantly and tends to be non-growing. Combine 2

In the graph, we can find the following rules:

1. The increase of magnet suction is directly proportional to the magnet volume.

2. The diameter has a great influence on the magnet suction and has a linear relationship.

3. When the diameter remains unchanged and the height of the magnet increases to a certain level, the suction hardly increases.

Fig. 1
Fig. 2