Re: Magnetic field and relative motion

From: Harry (harald.vanlintel_at_epfl.ch)
Date: 06/18/04 

Date: Fri, 18 Jun 2004 09:58:43 +0200

"V.K.Tamhane" <vktamhane12@rediffmail.com> wrote in message
news:9d62a326.0406150313.241a71b0@posting.google.com...

SNIP

> Let me refer to the actual experiment conducted.
> (J.W.Then,"Experimental study of the motional electromotive force",
> American journal of physics,30,411,1962).
> Refer fig.2. Disc shaped ceramic magnet M was placed in
> the brass cup F, co-axially. Magnetic flux was normal to the
> cylindrical side of the cup and parallel to the lead wire DE. It was
> observed that,
> 1. When cup alone was rotated, emf was produced.
> 2. When magnet alone was rotated there was no emf.
> 3. When the cup and the magnet were rotated together, emf was
> produced.

WHERE was it produced? In a co-moving meter? Not so if I understood well!

> Note that in 2 there is a relative motion and in 3 relative motion is
> zero. Placing contact E at various positions of the disc AB, emf
> remained unaltered, proving no emf was generated in the lead wires. (
> If you are still in doubt then you can simply extend the length of the
> cup, so that the stationary circuit is in the extremely weak field.)

> This expt. proves that relative motion plays no part.

I don't think so - Jorge Guala-Valverde et al, American Journal of Physics
70, oct.2002 p. 1052:
"The homopolar motor: a true relativistic engine".
"Relativistic" was imposed on him by the referees, but he himself does not
have the opinion that relativity has anything to do with it. He actually
meant relational, that is, working due to relative motion: "The unipolar
motor: A genuine relational engine" - Apeiron 4, oct.2001.

Harald

Relevant Pages

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