It is easy to confuse the two. After all, it is certain that heating will cause demagnetization of the magnet, and it is very simple to do the experiment! Then the temperature inside the earth is even as high as 6,000 degrees, and even the high-temperature-resistant magnets have demagnetized. Why does the earth still have a magnetic field that can protect itself? Where does this magnetic field come from?
To understand this problem, let's first briefly understand how the magnet is demagnetized! We all know that a magnet can be formed because the internal magnetic domain arrangement is consistent. We know that it is roughly the same, and if the direction is the same, there will be more people and more force. This is manifested in the macroscopic state that the substance is magnetic and can attract ferromagnetic substances... However, the thermal movement of molecules caused by high temperature heating will cause the magnetic domains to return to chaos, the magnetic moments of all parties will be offset, and the magnetism will disappear... But the magnetic properties will recover when the temperature drops, but not 100% recovery! And the temperature that causes the magnetic field to disappear is the Curie temperature, and the Curie temperature of different magnets is different!
Ferrite: around 450°C,
NdFeB: 320-380℃,
Alnico: 860-900℃
The most widely used NdFeB is actually the lowest, but according to the test, the magnetism of NdFeB begins to decline at 100 degrees Celsius, and it drops sharply at 150 degrees Celsius. As long as the NdFeB is kept for 20 minutes, it will be finished.. ....
But the inside of the earth is not a big magnet. Many schematic diagrams of the earth's magnetic field show a super large NS pole magnet. In fact, this is not a problem as a sign, but it is not rigorous enough, and it is easy to cause misunderstandings!
In fact, the magnetic field inside the earth is a dynamic magnetic field, and this magnetic field is produced by the dynamo effect!
There are many layers from the earth's crust to the earth's core. The rotation speed of the inner and outer layers caused by this iron-nickel fluid is different, and the geomagnetodynamo effect comes from this. Under the action of the initial magnetic flux, the outer layer The generated induced current flow will give an excitation mechanism to the core, and under this effect, the earth will have a normal magnetic field feedback and self-excitation mechanism, so the earth's magnetic field will continue to flow and never stop!
But there is a saying that since the 17th century, the earth's magnetic field has been weakening, and it may usher in a reversal, which will lead to a weak earth's magnetic field in the next few thousand years, or have a major impact on human production and life !
Because the solar wind will hit the ground directly, the by-product is the opportunity to see the aurora anywhere in the world! Do you still feel like watching the aurora?
