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Author Topic: re: Topic: What happens to aluminium in a magnetic field?  (Read 2281 times)

Offline germeten

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Hi, I have a question extension to post 4407 from 08/10/2010 by Chris. I understand that magnetism "doesn't like" aluminum, and repels it. Examples were given of levitating trains, etc., but my question goes a bit further, to wit, 1.) if a chunk of aluminum, say a billet, or cylinder, is placed inside an electromagnetic coil (obviously no core, other than the aluminum), how will the source current be affected? Will it go up, down or remain unchanged? 2.) Say we attached a wire lead to the aluminum core to ground, through a resistance/load, i.e. the aluminum is acting as a transformer secondary; in this case, same question(s) as #1. I watched a youtube video showing how such a setup can function as a diode for stepping down HV, but I still want to know how the source perceives it, as a drain on source, or not.


Offline evan_au

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I can't comment on the whole question, but there is a big difference whether the coil is fed from AC or DC:
  • If the coil is fed with AC, there will be an oscillating magnetic field. An aluminium bar sitting in the center will have eddy currents induced in it. Since aluminium is a good electrical conductor, these currents in the "secondary" will be quite high, the current in the coil will increase, and the aluminium will start to heat up
  • If the coil is fed with DC, there will be a static magnetic field. An aluminium bar sitting in the center will have no eddy currents, and so I expect that the current in the coil will be almost unchanged.

I don't see that a resistor or single wire to ground will change the current in the coil, provided the aluminium bar is electrically isolated from the coil? (Maybe a diagram might help explain the problem to the readers?)

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