There are three primary types of magnets: permanent magnets, temporary magnets, and electromagnets. Permanent magnets are materials that retain their magnetic properties over a long period without the need for an external magnetic field or electric current. Neodymium magnets are a well - known type of permanent magnet. They are made from an alloy of neodymium, iron, and boron and are extremely strong for their size. Neodymium magnets are widely used in applications where a powerful magnetic field is required, such as in headphones, speakers, and magnetic latches. Another example of a permanent magnet is the alnico magnet, which is made from aluminum, nickel, and cobalt. Alnico magnets have good temperature stability and are often used in applications where high - temperature resistance is needed, like in some industrial motors and sensors.

Temporary magnets, on the other hand, only exhibit magnetic properties when they are in the presence of an external magnetic field. Soft iron is a common material used to make temporary magnets. When a soft - iron bar is placed inside a coil of wire through which an electric current is flowing, it becomes magnetized. Once the current is turned off, the soft - iron bar quickly loses its magnetic properties. Temporary magnets are used in applications where the magnetic field needs to be controlled or turned on and off easily, such as in doorbells. When the doorbell button is pressed, an electric current flows through a coil, magnetizing a soft - iron core, which then attracts a metal striker to produce the ringing sound.

Electromagnets are created by passing an electric current through a coil of wire wound around a magnetic core. The strength of the magnetic field produced by an electromagnet can be easily adjusted by changing the amount of current flowing through the coil or the number of turns in the coil. Electromagnets are used in a wide range of applications, from simple devices like cranes that lift heavy metal objects in scrapyards to complex systems like particle accelerators in scientific research. In a scrapyard crane, a large electromagnet is used to pick up and move large pieces of iron and steel. By controlling the current, the operator can easily release the metal objects at the desired location.