The two are easy to confuse, after all, heating causes the magnet to demagnetize is already certain, and the experiment is very simple! Then the internal temperature of the earth is even as high as 6,000 degrees, and the magnets that are resistant to high temperatures have already demagnetized. Why does the earth still have its own magnetic field? Where does this magnetic field come from?
To understand this problem, let's first understand how the magnet is demagnetized! We all know that magnets can be formed because the internal magnetic domain arrangement is consistent and the same is obtained. When the direction is the same, people are more powerful. This is manifested in the macroscopic state that the material is magnetic and can attract ferromagnetic substances. However, the thermal motion of the molecules caused by high-temperature heating will cause the magnetic domain to return to chaos, the magnetic moments of all parties will cancel, and the magnetic properties will disappear. But the temperature will return to magnetic recovery, but it will not recover 100%! The temperature that causes the magnetic field to disappear is the Curie temperature, and the different magnets have different Curie temperatures!
Ferrite: about 450 ° C,
NdFeB: 320-380 ° C,
AlNiCo: 860-900 ° C
The most widely used NdFeB is actually the lowest, but according to tests, the magnetic properties of NdFeB begin to decrease at 100 degrees Celsius, and drop to 150 degrees, as long as the NdFeB is kept for 20 minutes. ....
But the interior of the earth is not a big magnet. Many of the earth's magnetic field diagrams are painted with a super large NS pole magnet. In fact, there is no problem as a gesture, but this is not rigorous enough, and it is easy to cause misunderstanding!
In fact, the magnetic field inside the earth is a dynamic magnetic field, and this magnetic field is produced by the generator effect!
There are many layers from the earth's crust to the core. The iron-nickel fluid causes different speeds of inner and outer rotation, and the geomagnetic generator effect is there. The outer layer is under the action of the initial magnetic flux. The induced current flow will give the core an excitation mechanism, and under this action, the earth will have a normal magnetic field feedback and self-excitation mechanism, so the earth's magnetic field will continue to flow, never stop!
But there is a saying that since the 17th century, the geomagnetic field has been steadily weakening, and perhaps there will be a reversal, which will lead to the weak magnetic field of the earth for thousands of years, or will have a major impact on human production and life. !
Because the solar wind will go straight to the ground, by-products have the opportunity to see the aurora anywhere in the world! Do you think there is still a feeling of watching Aurora?
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