According to the principle of electromagnetic induction, a strong current can generate a strong magnetic field, and a ferromagnetic substance is magnetized by a strong magnetic field. Since the magnetization characteristics of different substances are different, some substances are easily magnetized and are not easily demagnetized (loss of magnetism). It can retain magnetism for a long time. Magnetizing this material produces a magnet. Magnetize the hard magnet with a magnetizer.

According to the principle of electromagnetic induction, a current can generate a magnetic field, and a hard magnetic substance is magnetized by a strong magnetic field. Generally speaking, it is a magnetic material of a magnet. Actually, there are several different things: the most common magnet, such as a magnet for a general speaker, is iron. Neodymium magnet. They are iron scales (sheet-like iron oxides) which are detached from the surface of the slab rolling material during hot rolling in the steel mill. After removing impurities, pulverizing and adding a small amount of other substances, they are placed in a steel mold and pressure-molded. Then, it is sintered in a reducing electric furnace (through hydrogen), and some of the oxides are reduced to ferrite, cooled, and then placed in an exciter to be magnetized.