Composition and Properties
Magnets are composed of atoms such as iron, cobalt, and nickel. The internal structure of these atoms is rather special, and they inherently possess magnetic moments. Magnets are capable of generating magnetic fields and have the characteristic of attracting ferromagnetic substances like iron, nickel, and cobalt metals.
Types of Magnets
• Shape-based Magnets: There are various shapes including square magnets, tile-shaped magnets, special-shaped magnets, cylindrical magnets, ring magnets, disc magnets, magnetic rod magnets, and magnetic rack magnets.
• Attribute-based Magnets: SmCo magnets, Nd-Fe-B magnets (powerful magnets), ferrite magnets, Alnico magnets, and Fe-Cr-Co magnets.
• Industry-based Magnets: Magnetic components, motor magnets, rubber magnets, plastic magnets, and so on.
Magnets can be divided into permanent magnets and soft magnets. Permanent magnets are magnetized by a strong magnetic field, which makes the spins of magnetic substances and the electron angular momenta arrange in a fixed direction. For soft magnets, electricity is applied (which is also a way to apply magnetic force). Once the electric current is removed, soft iron will gradually lose its magnetism.
Poles and Directions
When the midpoint of a bar magnet is suspended with a thin string, at rest, its two ends will respectively point to the south and north of the earth. The end that points to the north is called the north-seeking pole or N pole, and the end that points to the south is called the south-seeking pole or S pole.
If we imagine the earth as a large magnet, then the geomagnetic north pole of the earth is actually the south-seeking pole, and the geomagnetic south pole is the north-seeking pole. Between magnets, like poles repel each other and unlike poles attract each other. Therefore, a compass repels the south pole, and a north-pointing needle repels the north pole, while a compass and a north-pointing needle attract each other.
Classification
Magnets can be classified into "permanent magnets" and "non-permanent magnets". Permanent magnets can be natural products, also known as natural lodestones, or they can be artificially manufactured. Non-permanent magnets, such as electromagnets, only exhibit magnetism under certain conditions.
