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  • photos on the refrigerator, watch television and work on the computer. Magnets come in a variety of strengths, shapes and sizes, and are made of different materials. Generally, magnets are broken down into three major categories, that is Permanent Magnets, temporary magnets and electromagnets. Ferrite Magnet , Cast AlNiCo Magnet , SmCo Magnet

    Permanent Magnets

  • Permanent magnets are the most common types of magnets, according to How Magnets Work. Permanent magnets, for example refrigerator magnets, retain a level of magnetism once they are magnetized. They are made of materials containing atoms and molecules with magnetic fields positioned to reinforce each other. Permanent magnets come in many shapes, such as balls, rectangular bars, horseshoes, rings and disks, according to Cool Magnet Man.

    Permanent Magnet Subcategories

  • There are four major types of permanent magnets, according to How Magnets Work. The subcategories are based on the composition of the magnet. Magnets in the first two categories, neodymium iron boron (NdFeB) and samarium cobalt (SmCo), are the strongest. They are considered rare earth magnets, since they come from the lathanoid (rare earth) series of elements on the periodic table. The third category, alnico magnets, are made from a compound of aluminum, nickle and cobalt. They are generally the weakest magnets, but they are least affected by changes in temperature. The final category, ceramic or ferrite magnets, is the most common. These magnets are generally strong, but their strength varies greatly depending on temperature.

    Temporary Magnets

  • Some materials act like magnets when they are in a strong magnetic field. This is called a temporary magnet, according to Cool Magnet Man. For example, paperclips and nails become temporary magnets when exposed to other magnets. However, they demagnetize when the permanent magnet is removed. Temporary magnets are used in telephones and electric motors, according to How Magnets Work.

    Electromagnets

  • Electromagnets are extremely strong magnets activated by electricity producing a magnetic field, according to How Magnets Work. Electromagnets feature a metal core (usually an iron alloy) surrounded by a coil of wire. When electricity flows through the coil, the current produces a magnetic field that magnetizes the core. An electromagnet changes polarity depending on which way the electric current is running. Electromagnets are used in televisions, computers, and cranes used to lift heavy metal for construction.