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Posted by D Sherman [72.47.153.24] on Monday, February 20, 2012 at 23:14:42 :
In Reply to: Re: Getting a metal sticker out posted by Jerry in Idaho [69.59.83.175] on Monday, February 20, 2012 at 23:02:38 :
There actually is such a thing -- sort of. They use them in recycling places to kick the non-ferrous metals off of the trash conveyor after a regular magnet has grabbed the ferrous trash. It's basically a strong induction coil that runs on AC and sets up "eddy currents" in the aluminum and brass. The magnetic field created by the eddy current repels the induction coil's current and causes the aluminum to move away from it. It sounds sort of magical but a very common application is the old-fashioned electric utility meters that have the rotating aluminum disk. Another demonstration is to get one of those super-strong magnets that's a ball about the size of a marble. If you drop it down a piece of 1/2" copper pipe it will move very slowly as if the pipe was full of gear oil, because as the magnet moves it sets up a current in the copper pipe that generates a magnetic field that repels the magnetic ball. If the copper was an absolutely perfect conductor, the ball would not drop at all.
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