Re: Faraday paradox redux

On Mon, 15 Sep 2008 12:07:34 -0700 Salmon Egg <SalmonEgg@xxxxxxxxxxxxx> wrote:
| In article <gal4q001i1f@xxxxxxxxxxxxxxxxx>, phil-news-nospam@xxxxxxxx
| wrote:
|
|> I say there is no EMF induced in the disk in this version of Faraday's disk.
|> Faraday measured current in this case, but that current was the result of
|> EMF induced in the wires connecting at the disk axle and at the disk edge
|> brush, from the moving magnetic field of the rotating magnets.
|
| I am not asking about a disk per se. The supposed paradox with a disk is
| that with the disk sandwiched in between magnets, there is no relative
| motion between the disk and the magnets engendering the field. The disk,
| however moves through the magnetic field an emf is induced.

The disk is not moving through a magnetic field in the case of the Faraday
experiment with rotating magnets attached to a rotating disk.


| I am now sandwiching a wire between two magnets. I try making the magnet
| large enough so to minimize fringe effects. If I move this sandwich
| normal to both the field direction and length of of the wire, does an
| emf get induced? Relativity would indicate that the magnetic field gets
| transformed (Lorentz transformation) from the motion to include an
| electrical field. What, if any, would be the difference of the
| environment of a point on the wire from a point on a Faraday disk
| sandwich?

If you are moving the magnets in sync with the wire, then there is no relative
motion and no EMF is induced. If the entire construction moves as a unit, then
we don't even need to address the "fringe field" issues.


| The yoke part may be a distraction, Think of a rectangular transformer
| core. Cut an gap through one leg for the magnetic field. Attach this to
| the magnets forming the sandwich. The only purpose for bringing this up
| was to confine the field to a well known volume rather than have to
| consider unknown fringing field.

I got the impression you said the whole thing moved as a unit all together.
If that is so, then the yoke is not even relevant and no EMF will be induced.

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Relevant Pages

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