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Q & A: currents in demagnetization

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Most recent answer: 08/14/2018
Q:
Someone told me that if a magnet is heated to beyond its Curie temperature, as the magnet loses its magnetic field there will be an induced electrical current in the metal of the magnet that slowly decays away due to the resistance of the metal. Is this true? If so, how does that happen?
- Dan S (age 37)
Canton, GA USA
A:

Yes, that happens. There's an electromotive force (like a voltage only it can go around a loop) proportional to the time derivative of the magnetic flux through a loop.Maxwell's equations, the basic rules of electromagnetism, say that has to happen. As the magnet demagnetizes, the field changes and thus so does the flux. That causes a current to flow.

This isn't really a deep explanation, because we haven't said why Maxwell's equations should be true. Maybe it will do for starters.

Mike W.

 


(published on 08/14/2018)

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