MadSci Network: Earth Sciences

Re: Do magnets ever run out of power?

Date: Tue Apr 30 12:22:41 2002
Posted By: Eder Molina, Researcher PhD, Dept. of Geophysics, Institute of Astronomy and Geophysics - USP
Area of science: Earth Sciences
ID: 1019211821.Es

In fact, the magnetic domains in a magnet may be affected by two main 
factors: temperature and external magnetic fields. Temperature can easily 
destroy the magnetic domains and transform your magnet in a piece of a 
mettalic alloy. You can think about it in the terms of the state of 
movement of the particles, that increase with temperature, and, at a 
certain level, "break" the magnetic domains. Each material has a 
temperature called Curie Temperature, above which no magnetic domains can 
exist. For hematite, for example, it is around 600-650 Celsius. But you 
don't have to reach this temperature to destroy partially the magnetic 
domains, so, if you expose your magnet at high temperatures, it will be 
gradually "losing power".
If you expose the material to a strong magnetic field the same effect can 
occur, because you are disturbing the alignment of the magnetic domains of 
the material.

If you take care with your magnet, I guess it will be in the family for 
many generations...  :)

Best regards

Eder C. Molina
Dept. of Geophysics
Institute of Astronomy, Geophysics and Atmospheric Sciences
University of Sao Paulo - BRAZIL

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