|MadSci Network: Physics|
In my classical experiments about the effect of temperature on magnets, we did not use magnets, because they are expensive and, after demagnetized, cannot get the fully magnetization again. So, we magnetised a steel blade, by using a strong magnet and pressing it against the blade, sliding in the same direction many times, until the material was magnetised, what we could see by attracting little metallic objects with it. Then, we began to heat this "home-made" or "school-made" magnet, and noticed that, as we increased the temperature, the material became non-magnetic at a certain temperature. In practice, we use a metodology similar to this to investigate the "fossil magnetic field" recorded in some rocky material (basalt, in most cases). If we are under normal temperature, the magnetic domains are strong enough to mantain the preferential direction of magnetization, and the rock behaves as a magnet. If we heat the material, the thermal effects conterparts the magnetic intrinsic force in the material, until at the Curie temperature (about 600-800 Celsius for most magnetic minerals), the heat destroys the magnetic domains, and the material behaves as a non-magnetic mineral. Of course, this kind of experimentation is done with very sensible equipment and techniques, but I've described it just to illustrate an application of this experiment in the real world. I think you could try to using some metallic (iron made) material to magnetized and them demagnetize them. If you do so, you are showing interesting effects about magnets (that some materials can obtain magnetization when exposed to strong magnetic fields, that the temperature conterparts this effect, and can even remove the magnetization of a magnet). Best regards Eder C. Molina firstname.lastname@example.org Dept. of Geophysics Institute of Astronomy and Geophysics University of Sao Paulo BRASIL
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