Re: is the magnetic field really moving?

On Mon, 25 Aug 2008, Salmon Egg wrote:

> After reading all the posts here on this subject, I do not expect to 
> find any more insight. Before throwing in the towel, I will try asking a

> question once more.
> 
> Given a uniform and circularly symmetric cylindrical bar/disk magnet 
> spinning on it axis, how can the rotation of the magnet be detected by 
> observing properties of the magnetic field alone?

This is an entirely different question from ones about whether the field 
moves/rotates.

For small v^2/c^2, the magnetic field is the same for the rotating and 
stationary magnet, so, strictly speaking, the rotation can't be detected 
from observing properties of the magnetic field alone.

Why restrict it to the magnetic field only? The rotating permanent magnet 
is covered well in Van Bladel, Relativity and engineering, pp 296-298. A 
unipolar generator uses the electromagnetic field to detect the rotation 
quite well indeed.

What kind of insight were you hoping for? The various phenomena are 
well-described by existing theory - the electromagnetics of rotating 
media is known (but isn't covered in many books).

-- 
Timo Nieminen - Home page: http://www.physics.uq.edu.au/people/nieminen/
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