Discovery and development of magnets
Magnet is not invented by man, it is natural magnetite. The ancient Greeks and Chinese discovered a kind of naturally magnetized stone in nature, which they called "magnets". This kind of stone can magically attract small pieces of iron, and always point in the same direction after swinging at will. Early navigators used this magnet as their earliest compass to identify directions at sea. It should be the Chinese who first discovered and used magnets, that is, using magnets to make "compass", which is one of the four great inventions of China.
After thousands of years of development, magnets have become powerful materials in our lives today. By synthesizing alloys of different materials, the same effect as the magnet can be achieved, and the magnetic force can also be improved. Man-made magnets appeared in the 18th century, but the process of making stronger magnetic materials was slow until the creation of aluminum nickel cobalt (Alnico) in the 1920s. Subsequently, ferrite (Ferrite) was produced in the 1950s, and rare earth magnets [Rare Earth magnet, including neodymium iron boron (NdFeB) and samarium cobalt (SmCo)] were produced in the 1970s. So far, magnetic technology has developed rapidly, and strong magnetic materials have also made components more miniaturized.
In 1822, French physicists Arago and Lussac discovered that when an electric current passes through a winding with iron in it, it can magnetize the iron in the winding. This is actually the original discovery of the principle of electromagnets. In 1823, Sturgeon also did a similar experiment: he wound 18 laps of bare copper wire on a U-shaped iron rod that was not a magnet rod. The copper coil on the U-shaped iron rod produces a dense magnetic field, so that the U-shaped iron rod becomes an "electromagnet". The magnetic energy on this kind of electromagnet is much larger than that of the permanent magnet, and it can absorb iron blocks 20 times heavier than it.It couldn't absorb it either, and became an ordinary iron rod again. Sturgeon's invention of the electromagnet made people see a bright prospect of converting electrical energy into magnetic energy. This invention quickly spread in Britain, the United States and some coastal countries in Western Europe. In 1829, the American electrician Henry made some innovations to the Sturgeon electromagnet device. Insulated wires replaced bare copper wires, so there was no need to worry about being short-circuited by copper wires too close. Since the wires have an insulating layer, they can be tightly wound together round and round, and the denser the coil, the stronger the magnetic field generated, which greatly improves the ability to convert electrical energy into magnetic energy. In 1831, Henry trial-produced a newer electromagnet. Although it was not large in size, it could absorb a 1-ton iron block. The invention of the electromagnet also greatly improved the power of the generator.
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--------Mr. Tae Lee Korea
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