Although magnetism is invisible and untouchable, it is also a special substance that exists objectively. One essential characteristic of a magnet is its magnetism, as it is one of the factors that users use to determine the quality of a magnet. Magnetism and magnets are interactive media with a bit of mystery, but they affect our lives. How did the magnet come from?
The reason why magnets can generate magnetic fields can be explained from two aspects:
1、 Based on motion current
Electric field and magnetic field are two sides of Electromagnetic tensor, and they are interrelated. When the relative velocity between the observer and the charge changes due to different Frame of reference, the Electromagnetic tensor may split into the electric and magnetic fields generated by the moving charge.
2、 Based on spin, the quantum characteristic of Elementary particle
The magnetism in ferromagnetic materials based on spin. Firstly, one point needs to be clarified. Because spin is an essential property of some Elementary particle (such as electrons) that make up matter. Therefore, theoretically speaking, all substances have "magnetism". The difference is that different substances exhibit different types of magnetism. And what we commonly refer to as a "magnet" mainly refers to a "ferromagnetic substance" that has independent (no external field) magnetic energy (magnetic field), that is, a permanent magnet.
Simply summarize the above:
The attraction of iron by a magnet is determined by its characteristics. If explained by atomic current, it is the magnetic field generated by the current that magnetizes other objects, producing an electric field. The interaction of electric fields and electric fields generates forces.
Most substances are composed of molecules, which are composed of atoms, and atoms are composed of nuclei and electrons. Within an atom, electrons constantly rotate and revolve around the nucleus. Both of these movements of electrons generate magnetism. But in most substances, the directions of electron motion are different and disorderly, and magnetic effects cancel out each other. Therefore, most substances do not exhibit magnetism under normal circumstances.
Ferromagnetic materials such as iron, cobalt, nickel or ferrite are different. The internal electronic spins can be spontaneously arranged in a small range to form a Spontaneous magnetization region, which is called a magnetic domain. After magnetization of ferromagnetic materials, the internal magnetic domains are arranged neatly and in a consistent direction, strengthening the magnetism and forming a magnet. The process of attracting iron by a magnet is the magnetization process of the iron block. The magnetized iron block and the magnet generate attraction between different polarities, and the iron block firmly "sticks" to the magnet. We say that magnets have magnetism, which is the source of the magnet.