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Re: jumping ring demo



At 07:18 3/8/01 -0500, Eugene Mosca wrote:

Check the article "A Classroom Jumping Ring," by Carl Schneider and John
Ertel in American Journal of Physics, Volume 66, Issue 8 pp. 686-692
(August 1998). /snip/

Also, there was a jumping ring entered into the 1999 AAPT apparatus
competition. Construction details are available at:

<http://www.rose-hulman.edu/~moloney/AppComp/1999Entries/entry02.htm#RngShoo
ter>

Gene

These were some really useful cites. Though there are plenty of
jumping rings shown as physics demos on the net, references to
ampere-turns and core areas are lacking. The Stillwater people
apparently based an OSU design on Schneider/Ertel's Navy model.
I include a URL containing a detailed description from
Stillwater below, as a proxy for Schneider and Ertel's jumping ring
configuration. This may help people like me who can't put hands on
the Aug 88 AJP.

<http://elec-engr.okstate.edu/ecen3613/McClatchey/madison.htm>


In contrast, the Rose-Hulman instance that Gene mentioned,
appeals to a design principle that has a certain engineering
logic: brute force!
The instructions include these immortal lines;
'Tune the core to coil until the AC current rises from 8 amps
to 60 amps. The thermal breaker will drop in a second or so....'
or words to that effect. :-)
Now *that's* a ring shooter!


Two tips and tricks are hinted at in various decriptions: ring
thickness should be a good multiple of effective skin depth to
maximize phase shift.
And core magnetic field divergence is helpful.

This is another of those deceptively simple engineering objects like
the screw jack where Feynman strayed with his Lectures on Physics,
omitting the crucial functional element in the process (phase lag
in the ring).

Scientific American's Amateur Scientist column carried one of Professor
Stong's typically fascinating pieces in the August 1961 issue.
The fresh twist on the topic was a series capacitor to tune the coil to
about 55Hz. Then the ring's position on the core affects the inductance
and hence resonance, so that the ring oscillates slowly up and down
the column.
He continues with another negative impedence effect: a choke (i.e the
primary coil of a mains transformer), a capacitor and an incandescent
lamp across the mains. That arrangement will oscillate, flashing the lamp
every few seconds if (and only if) the feed voltage is carefully
tuned with a variac, in order to locate the negative impedance
characteristic offered by the transformer winding as the current rises
towards saturation.

Straying off-topic....
While reviewing hits from searching on Schneider-Ertel's ring jumper,
I saw in a PDF summary of research endeavors from the Naval academy,
a method for ...shall I say?... establishing the Earth's
velocity vector in a reference frame provided by three
relatively orthogonal pulsars, whose emissions need only be recovered
from a signal 100 orders of magnitude under the ambient noise - I
assume by cross correlation or synchronous detection methods, then
evaluating their Doppler contributions. This seems to be in the same
big league as resolving the integrated surface breathing and motional
modes of the Sun using Sodium hyperfine line doppler shift.
A coup de science, in fact.

Brian

I have tried to build one of the Jumping ring demo's and have met with
some difficulty. /snip/

P. Lohstreter




brian whatcott <inet@intellisys.net> Altus OK
Eureka!