Date: Fri, 25 Oct 2002 15:24:52 -0400 (EDT)

Author: Steve Wonnell

Subject: Re: Einstein-de Haas effect demonstration

Post:


So the material magnetizes, and, because it is now magnetized,
precesses in the external field, if the coil current is DC? And its
magnetization, and the direction of precession, reverses when the external
field is reverses, resulting in oscillations if the external field is AC?


On Fri, 25 Oct 2002, George Weremczuk wrote:

> The Einstein-de Haas effect: An unmagnetized ferromagnetic material is
> suspended within a coil of wire. The net spins of the atoms (due to unpaired
> electrons in the outer orbit) within the material are initially oriented in
> random directions. When a current passes through the coil, the magnetic field
> in the center of the coil causes the atomic spins within the ferromagnetic
> material to all orient in the same direction, resulting in a net angular
> momentum for the sample. The sample will rotate about an axis parallel to the
> direction of the magnetic field. If an alternating current passes through the
> coil, the ferromagnetic material will oscillate about that axis.
>
> It sounds like a simple setup but it is unclear what the best material would be
> and how strong the magnetic field needs to be to reorient the atoms enough for
> the effect to show.
>
> Wolfgang Rueckner wrote:
>
> > Please elaborate on these a bit. I'm not familiar with these
> > effects. Wolfgang
> >
> > >Does anyone do a lecture demonstration of the Einstein-de Haas effect also
> > >sometimes known as the gyromagnetic effect? It seems like it would be easy
> > >to demonstrate but I have been unable to find a description of suitable
> > >apparatus. I would appreciate either a desciption and/or plans of
> > >someone's successful demonstration or references for appropriate
> > >apparatus. Thank you.
> > >
> > >::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
> > >:: GEORGE WEREMCZUK gweremczuk@cariboo.bc.ca ::
> > >:: Physics Laboratory Faculty Phone: (250)828-5448 ::
> > >:: Department of Physical Sciences Fax: (250)828-5450 ::
> > >:: University College of the Cariboo ::
> > >:: Box 3010 ::
> > >:: Kamloops, BC V2C 5N3 ::
> > >:: CANADA ::
> > >::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
>
>


************************************************************************
Steven K. Wonnell
Physics and Astronomy Department E-Mail: wonnell@pha.jhu.edu
Johns Hopkins University Phone: (410) 516-4696, 516-5468
3400 N. Charles Street Fax: (410) 516-7239
Baltimore, MD 21218-2686 Office: 478 Bloomberg
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