Why do magnets suck iron? What's the principle?
Magnetism is one of the basic properties of matter. All substances are magnetic media. Divided into three types:
One. Paramagnetic material, which produces the same additional magnetic field as the external magnetic field under the action of a magnetic field, and most of the substances fall into this category.
Two. A diamagnetic material that produces an additional magnetic field, such as copper and inert gas, that is opposite to the external magnetic field under the action of a magnetic field.
3, ferromagnetic material, which produces the same strong additional magnetic field as the external magnetic field under the action of a magnetic field, such as iron cobalt nickel. According to the hypothesis first proposed by Ampere, there is a permanent molecular current with a certain magnetic moment in the paramagnetic molecules. In the absence of an external magnetic field, the orientation of these molecular currents is irregular due to the thermal motion of the molecules. Therefore, the magnetic field generated by them is equal to zero and does not show magnetic properties externally. When there is an external magnetic field, these molecular currents are subjected to the orientation of the outer field, and their magnetic moment lattice turns to the direction of the external magnetic field. An additional magnetic field is generated along the direction of the external magnetic field. The molecules that make up the antimagnetic mass, in the absence of an external magnetic field, the internal structure of the molecules makes their molecular current equal to zero. When the external magnetic field is introduced, the induction current is generated when the magnetic field is introduced into the closed circular wire. In these anti-magnetic molecules, induction currents are also specialized. Because there is no resistance in the molecule, as in superconductors, currents once generated will always circulate until the reverse induction current is offset by it when the external magnetic field is old. Under the action of an external magnetic field, all magnetic media must generate induced molecular currents, that is, diamagnetism is common to all substances, but in a paramagnetic molecule, the magnetic moment of the molecular current is much larger than that of the induced current. Much larger, Therefore, the diamagnetic properties of the material are concealed and only paramagnetic properties occur. The cause of ferromagnetism has a magnetic domain hypothesis: the magnetic moment of a single atom of many substances is on an order of magnitude, so it is not the magnetic moment of the atom that is affected by the magnetic field that causes the ferromagnet and other magnetic media. difference. It is because the atoms of the ferromagnet are more easily arranged under the action of the external magnetic field. Why is the atomic magnetic moment in a ferromagnet so easily arranged? This is because there is a molecular field in the ferromagnet due to the strong interaction between atoms(called the exchange force). The molecular field acts like a magnetic field, causing the orientation of the atomic moment to be arranged and the size of the molecular field., The magnetic field is much stronger than the ordinary one. For example, at room temperature, more than 95 % of the original magnetic moments are arranged in an orientation due to the action of the molecular field. However, ferromagnets do not exhibit magnetism before they are magnetized. This is because each ferromagnet is actually divided into many small areas. We call such a small area a magnetic domain. The molecular field makes each of the magnetic domains original. The magnetic moments are arranged in the same direction. However, the magnetic moment directions of each magnetic domain are different from each other. Therefore, in the absence of an external magnetic field, although the original magnetic domains of each magnetic domain are almost all arranged in the magnetic short, the total magnetic short of the iron body is still zero, and the entire ferromagnet does not appear. Magnetism. After adding the external magnetic field, The direction of the magnetic moment of each magnet turns to the direction of the external magnetic field, and the total magnetic moment of the ferromagnet is not zero. Since the original magnetic moment in each nourishing domain has been oriented when there is no external magnetic field, the iron nourishing body is not large. Strong magnetism is also shown in the external magnetic field. When the temperature is higher than one value(Curie point), the magnetic domain disintegrates and loses the ferromagnetic properties, which are the same as ordinary paramagnetic substances.