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Re: [Phys-l] drop a metal cylinder through a solenoid



On 3/21/2012 4:17 PM, Carl Mungan wrote:
If we drop a permanent magnet through an aluminum pipe, the magnet
falls slowly due to eddy current loops induced above and below the
falling magnet.

What if one instead drops an aluminum cylinder through a solenoid
(having a constant current): Will the cylinder fall (significantly)
slower than with the current off?

If this has never been tried before experimentally to anyone's
knowledge, I'll try to set it up and see. But first I thought I'd ask
if either anyone has tried it or can make a definite prediction about
the answer?
This seems like a straight forward experimental question, to which, as far as I know, the answer is yes.
The reason goes like this: Helmholtz found that two narrow coils spaced at (if I recall) a diameter apart,
provide a sensibly uniform field for an appreciable part of the contained volume.
This being the case, a continuous solenoid of the same diameter as length would have a non
uniform internal field. This would provide modest eddy currents in a conductive cylinder dropped within.

Brian W