Permanent magnets retain their magnetic properties over a long period without the need for an external power source. The four common types mentioned above, neodymium, ferrite, alnico, and samarium - cobalt magnets, all fall into this category. Permanent magnets are created by heating a ferromagnetic material, such as iron, nickel, or cobalt, in the presence of a strong magnetic field. This aligns the magnetic domains within the material, causing it to become magnetized. Once magnetized, the material will continue to produce a magnetic field on its own. Permanent magnets are used in a wide variety of applications, from simple household items like refrigerator magnets to complex industrial machinery and high - tech electronics.

Electromagnets

Electromagnets, on the other hand, generate a magnetic field only when an electric current passes through a coil of wire. The strength of the magnetic field can be easily controlled by adjusting the amount of current flowing through the coil. Electromagnets are used in many applications where variable magnetic fields are required. In cranes used for lifting heavy metal objects in scrapyards, large electromagnets can be turned on and off to pick up and release the metal. In particle accelerators, electromagnets are used to guide and focus beams of charged particles. They are also an essential part of electric motors and generators, where the interaction between the magnetic field of the electromagnet and the electric current in the coils produces mechanical motion or electrical energy.

Temporary Magnets

Temporary magnets can be magnetized when they are placed in a strong magnetic field but lose their magnetism when the external field is removed. Soft iron is a common material used to make temporary magnets. Temporary magnets are used in applications where a magnet is needed only for a short period. For example, in some doorbells, a temporary magnet is used to attract a metal clapper to produce the ringing sound when an electric current passes through a coil, creating a magnetic field. Once the current stops, the magnetism in the soft iron fades, and the clapper returns to its original position.