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FERROMAGNETIC MATERIALS

After reading this section you will be able to do the following:

  • Explain the differences between a permanent magnet and a temporary.
  • Explain why some materials have magnetic properties only when a permanent magnet is near them.

Questions

  1. What is happening in this experiment?
  2. What conclusions can you draw about magnets and magnetism from this experiment?

How does an object become a magnet?

We have determined in previous discussions that magnets can be permanent or temporary. A permanent magnet is more difficult to magnetize but will retain the properties of magnetism indefinitely. A temporary magnet is generally made of soft iron and will remain magnetized only as long as the magnetizing cause is present. From previous experiments you saw how the difference in magnetized and unmagnetized material depends on the motion and arrangement of the material's molecules. Bringing a ferromagnetic object, like a nail, into the magnetic field of a strong magnet can cause the molecules of the iron material to line up and the nail to become a temporary magnet. As long as it is in the magnetic field of the bar magnet, the nail acts like a magnet and picks up other ferromagnetic materials. In this case it is the paper clip. Then, the paper clip becomes a magnet and can pick up another paper clip, and so forth.