Magnetic field infiltration will harm the central nervous system, cardiovascular system and so on. , and has an important impact on biological growth, life activities and behavior habits.
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Magnets are not invented by people, but natural magnetite. The ancient Greeks and China discovered that there was a naturally magnetized stone in nature, called a "magnet". This kind of stone can magically pick up a small piece of iron and swing it at will and always point in the same direction.
Early navigators used this magnet as their earliest compass to tell directions at sea. China was the first to discover and use magnets, that is, making a compass with magnets is one of the four great inventions in China.
After thousands of years of development, magnets have become a powerful material in our life today. By synthesizing alloys of different materials, we can achieve the same effect as magnets and improve the magnetic force.
/kloc-artificial magnets appeared in the 0/8th century, but the process of making stronger magnetic materials was very slow, and Al-Ni-Co was not produced until the 1920s. Subsequently, ferrite was manufactured in 1950s and [rare earth magnets [including NdFeB and SmCo]] was manufactured in 1970s. At this point, magnetic technology has developed rapidly, and ferromagnetic materials have also made components more miniaturized.
References:
Baidu encyclopedia-magnet