Re: Lenz's Law?

[trappe@PHYSICS.UTEXAS.EDU (Karl Trappe)]

> > >  Also, he said the demonstration where an aluminum ring is placed on
> > >  an iron core stand that is surrounded by a transformer coil does not >
> > > truly demonstrate Lenz's Law.  What is your sense on this one, too.
> >
> > What is demonstrated with the aluminum ring?  I know of a couple of
> > things:


Ahh, the joys of being a member of PIRA!!!

> From the ten years work known as the "Physics Demonstration Bibliography":
The PIRA (Physics Instructional Resource Association) identification for
the demo in question is 5K20.30 jumping ring.

References are:
(1)  Sutton Demo # E-236 (Solid and split aluminum rings on the vertical
transformer)
(2)  Frier & Anderson Demo # Em-12 (An aluminum ring jumps off the iron
core of a vertical inductor)
(3)  The Video Encyclopedia of Demonstrations Disk 20-18 (A copper ring
levitates, an aluminum ring flies off, a slit ring does nothing, and a
coled ring flies higher)
(4)  Meiners Demo # 31-2.9 (Be careful how you analyze the jumping ring)
(5)  AJP 39(3), 285 (An analysis of the role of phase difference in the
levitating ring demonstration)
(6)  AJP 54(9), 808 (An analysis of the role of phase difference in the
levitating ring demonstration)

Enjoy, Karl

Dr. Karl I. Trappe                              Desk Phone:  (512) 471-4152
Physics Dept, Mail Stop C-1600                  Demo Office: (512) 471-5411
The University of Texas at Austin               Home Phone:  (512) 264-1616
Austin, Texas 78712-1081