How Everything Works
How Everything Works How Everything Works
 

QUESTIONS AND ANSWERS
 
Question 846

Do regular magnets lose their magnetism or do they stay magnetized always? What about electric magnets, like the ones used in wrecking yards? — KM, Delta, British Columbia
Permanent magnets are made from materials with two important magnetic characteristics. First, these materials are intrinsically magnetic, meaning that some of the electrons in these materials retain their natural magnetism. While electrons are always magnetic, that magnetism is lost in most materials because of complete cancellations—each magnetic electron is paired with another magnetic electron so that they cancel one another perfectly. However, there are some materials in which the cancellation is imperfect and these materials (including iron, cobalt, nickel, and many steels) are the basis for most permanent magnets.

Second, the materials used in permanent magnets have internal structures that make the magnetic electrons align along particular directions. Once the electrons are aligned along one of those directions, they stay aligned and the material exhibits strong magnetic characteristics. It becomes a "permanent magnet."

A permanent magnet remains its magnetization as long as nothing spoils the alignments of its magnetic electrons. These electrons can be knocked out of alignment by vibrations, heat, or other magnets. If you hit a permanent magnet with a hammer or heat it in the oven, you will change and perhaps destroy its magnetization. This magnetization can be recovered by exposing the permanent magnet to the magnetic influences of an electric current. In fact, permanent magnets are originally magnetized by placing them near electric currents that align their magnetic electrons. Moreover, even a material that doesn't have the internal structures needed to keep its electrons aligned along a particular direction will become magnetized temporarily by placing it near an electric current. That's how a wrecking yard magnet works-an electric current temporarily turns a large piece of iron into a strong magnet.

         

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