Wes Johnston wrote:
>
> Last time I was in Germany at the Deutsches Museum in Munich, I saw a steel
> ball about 1 inch in diameter suspended in a magnetic field.  The electro
> magnet would come on full force and as the ball rose, it would interrupt a
> light beam causing the magnet to switch off.  Very simple.  Very power hungry.

If instead a steel ball it was just a rod magnet, the power consume
would be sensible smaller, since the critical position to interrupt the
electro-magnet would be when the rod magnet is also acting its field
over the electromagnet itself, so canceling a lot of gravity effect.  An
interesting device could be done using a brushless dc motor coils, and
rotate the field, so the suspended magnet would rotate too... :)  A wide
assembly of those coils could make the suspended magnet not only rotate,
but move in an orbital shape since it will try to get out in its
tangencial vectors (centrifugal force).

Wagner.