Why magnets attract iron?
The magnet is an iron suction stone, have you ever played with it yet? Using magnets can attract iron objects such as nails, needles, etc., which is very interesting. Why magnets can attract iron? That must be explained from the molecular structure of the material onwards.
All matter is made up of molecules. Molecules are made up of atoms, and atoms are made up of atomic nuclei and electrons. The electron is constantly spinning in the atom and orbiting the atomic nucleus. Those two types of electrons can generate magnetism. However, in the vast majority of matter, the electron’s direction of motion is not the same, messy and chaotic. That makes the magnetic effect of internal matter cancel each other out. Therefore, under normal circumstances, the majority of matter does not exhibit magnetism.
And magnets are not like that. Magnets are generally due to ferromagnetic materials such as iron, cobalt, nickel or ferrite etc. make into. The magnet’s magnetism comes primarily from the rotation of electrons.
In ferromagnetism, the spontaneous rotation of the electron can spontaneously arrange in a small range, i.e. all electrons in the atom within that small range retain the same rotation direction, forming a small magnetizing region. spontaneous. This type of spontaneous magnetized region is called the magnetic domain (magnetic domain). The size of the magnetic domain is not the same. In short, each magnetic domain occupies a volume of about 109 cm3, containing about 1015 atoms. Because the magnetic directions of all atoms in a magnetic domain are uniform, the result of superposition is mutual reinforcement. A magnetic domain is equivalent to a “small magnet”, which is made up of such a large number of “small magnets”.
Before the magnetization, the magnetic orientation of all magnetic domains in the ferromagnetic material is not the same, not coordinated with each other. As a result, other magnetic fields cancel each other out, to the outside they still do not show magnetism. However, after applying strong external magnetic fields, they rearrange in the direction of the magnetic field. We say ferromagnetic is magnetized. It immediately turned into a magnet. But, in other materials when placed in a magnetic field, the electrons in the atom do not obey “orders” but “line up”, still moving in chaos. These are non-magnetic materials like copper, aluminum, lead and so on. There the electrons are like a bunch of disobedient children, even if they apply a stronger external magnetic field, they still move in disarray at will. So these materials cannot be magnetized, that is, they are non-magnetic.
The reason magnets attract iron is because magnets are magnetic. When near the iron, the magnet’s magnetic field causes the lump to magnetize. Between the different poles of the magnet and the lump produces a pull, the lump “sticks” tightly to the magnet. But metals like copper, aluminum, lead etc. cannot be magnetized by a magnet, cannot produce magnetism, so magnets are helpless against them.
Permanent magnets that we often encounter there are two types: artificial magnets and natural magnets. Artificial magnets are made by putting ferromagnetic material into the magnetic field, making it magnetized. After withdrawing the external magnetic field, the electrons in the ferromagnetic material still maintain the “whole line”, exhibiting strong magnetism for the outside. And natural magnets are a kind of iron ore stone in nature, under the magnetizing effect of the Earth’s magnetic field, it has permanent magnetism.