Date: Sat Nov 4 11:38:30 2006

Author: Urs Lauterburg

Subject: Re: jumping rings "launcher" and load

Post:
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Krishna and other jumping ring Tap-lers,

The jumping ring demo does indeed represent some electrodynamic
mechanisms which at least I myself don't fully understand either. It
has always puzzled me that the ring wold jump so much higher when
immediately switching the coil to a 230VAC outlet as opposed to
switching it onto a DC source capable to supply a good current as
well. In my opinion this has to do something with the inductive
resistance and the timing properties in the two different cases. It
would indeed make for a nice paper in the Physics Teacher or alike
to investigate the behavior in details. All it actually needs is a
good basic understanding of resistivity and inductance plus the
Lenz's law which makes the ring take off. Dynamic measurements of the
currents, voltages, and magnetic field strengths should explain the
mechanisms which are involved. However, maybe such a document does
allready exist somewhere. Would you know?

One just simply has to find time for investigation and that is my
problem at the moment. I am working under full load and I am always
glad to make it to the next weekend, one of which is right now!

And yes, Jerry Z. is of course right when he bring in the inductive
property of the coil to explain why the fuses don't blow. Measuring
current is one thing but if the instrument does not take phase
difference between current and voltage into account you will read
imaginary portions as well. In this sense a fuse is a better
indicator of the real current that has actually flown through.

This entire topic is of special interest when driving Tesla Coils.
That's where it's really important to keep the timing and the flow of
energies under control to make those things spark madly.

See a complete documentation (Sorry it's in my native German language
only) of the lovely Twin Tesla Generator I have realized with my dear
coiler friend Kurt Schraner at:

http://home.tiscalinet.ch/m.schraner/UBTT-Betrieb.pdf

You might also find nice information about the behavior of coils on
Kurt Schraner's web site at:

http://home.datacomm.ch/k.schraner/index.htm

Regards and happy demoing physics

Urs

Urs Lauterburg
Physics demonstrator
Physikalisches Institut
University of Bern
Switzerland

>On 11/2/06, Richard Heckathorn
> wrote:
>
>My circuit breaker is a piece of aluminum foil. I put a couple of
>bar magnets in the coil, push the on switch, the fuse blows and the
>bar magnets are magnetized.
>
>
>Dick, thanks for replying. Actually, it is this idea that I want to
>test out. In the most recent issue of The Physics Teacher,
>(November 2006, p. 524) is an article entitle "A Magnetic Paradox"
>which introduced me to an idea I had never heard of before:
>remagnetizing a demagnetized bar magnet using AC. That made no
>sense to me - one uses AC to *demagnetize*, on average (like a
>degausser for CRT screens). This article refers to two earlier
>notes in The Physics Teacher: March 2003, p. 185 and March 2004, p.
>182.
>
>The March 2004 note is just what Dick describes above and on his
>website. Upon reading, this method makes sense to me. The fuse
>acts in essence to rectify the circuit. The current rises, and at
>some value, the fuse blows. So it's not really AC, and the huge
>pulse of current results in a very large magnetic field that points
>in one direction and never reverses direction. So it makes sense to
>me that this method would result in remagnetization: the very large
>magnetic field realigns the domains that have randomized due to
>time, thermal effects or mechanical shock.
>
>But the March 2003 TPT note claims that you can remagnetize a bar
>magnet with an actual AC field. That makes no sense to me, but I
>wanted to test it for myself. The setup decribed is an old PSSC air
>core solenoid spliced into a plug. Hence my original question - it
>didn't seem safe to me. But if I read Dale's message correctly,
>that is essentially what they are doing at Iowa (with a variac ).
>
>Has anyone ever seen this remagnetization of a magnet using an AC
>current through an air core solenoid? I did try a preliminary
>experiment using our jumping ring setup and got some interesting
>results, but nothing convincing. My initial thought is that I just
>happened to pulse the AC right so that sometimes I turned it off at
>max current and thus max field.
>
>Thanks again.
>
>--
>regards
>-Krishna
>
>Krishna Chowdary
>Department of Physics & Astronomy
>Bucknell University

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Krishna and other jumping ring Tap-lers,

The jumping ring demo does indeed represent some electrodynamic
mechanisms which at least I myself don't fully understand either. It
has always puzzled me that the ring wold jump so much higher when
immediately switching the coil to a 230VAC outlet as opposed to
switching it onto a DC source capable to supply a good current as
well. In my opinion this has to do something with the inductive
resistance and the timing properties in the two different cases. It
would indeed make for a nice paper in the Physics Teacher or
alike to investigate the behavior in details. All it actually needs is
a good basic understanding of resistivity and inductance plus the
Lenz's law which makes the ring take off. Dynamic measurements of the
currents, voltages, and magnetic field strengths should explain the
mechanisms which are involved. However, maybe such a document does
allready exist somewhere. Would you know?

One just simply has to find time for investigation and that is my
problem at the moment. I am working under full load and I am always
glad to make it to the next weekend, one of which is right now!

And yes, Jerry Z. is of course right when he bring in the inductive
property of the coil to explain why the fuses don't blow. Measuring
current is one thing but if the instrument does not take phase
difference between current and voltage into account you will read
imaginary portions as well. In this sense a fuse is a better indicator
of the real current that has actually flown through.

This entire topic is of special interest when driving Tesla
Coils. That's where it's really important to keep the timing and the
flow of energies under control to make those things spark madly.

See a complete documentation (Sorry it's in my native German language
only) of the lovely Twin Tesla Generator I have realized with my dear
coiler friend Kurt Schraner at:

http://home.tiscalinet.ch/m.schraner/UBTT-Betrieb.pdf

You might also find nice information about the behavior of coils on
Kurt Schraner's web site at:

http://home.datacomm.ch/k.schraner/index.htm

Regards and happy demoing physics

Urs

Urs Lauterburg
Physics demonstrator
Physikalisches Institut
University of Bern
Switzerland

On 11/2/06, Richard Heckathorn wrote:
My circuit
breaker is a piece of aluminum foil. I put a couple of bar magnets in
the coil, push the on switch, the fuse blows and the bar magnets are
magnetized.



Dick, thanks for replying. Actually, it is this idea that I want
to test out. In the most recent issue of The Physics Teacher,
(November 2006, p. 524) is an article entitle "A Magnetic
Paradox" which introduced me to an idea I had never heard of
before: remagnetizing a demagnetized bar magnet using AC.
That made no sense to me - one uses AC to *demagnetize*, on average
(like a degausser for CRT screens). This article refers to two
earlier notes in The Physics Teacher: March 2003, p. 185 and
March 2004, p. 182.

The March 2004 note is just what Dick describes above and on his
website. Upon reading, this method makes sense to me. The
fuse acts in essence to rectify the circuit. The current rises,
and at some value, the fuse blows. So it's not really AC, and
the huge pulse of current results in a very large magnetic field that
points in one direction and never reverses direction. So it
makes sense to me that this method would result in remagnetization:
the very large magnetic field realigns the domains that have
randomized due to time, thermal effects or mechanical shock.

But the March 2003 TPT note claims that you can remagnetize a bar
magnet with an actual AC field. That makes no sense to me, but I
wanted to test it for myself. The setup decribed is an old PSSC
air core solenoid spliced into a plug. Hence my original
question - it didn't seem safe to me. But if I read Dale's
message correctly, that is essentially what they are doing at Iowa
(with a variac ).

Has anyone ever seen this remagnetization of a magnet using an AC
current through an air core solenoid? I did try a preliminary
experiment using our jumping ring setup and got some interesting
results, but nothing convincing. My initial thought is that I
just happened to pulse the AC right so that sometimes I turned it off
at max current and thus max field.

Thanks again.

--
regards
-Krishna

Krishna Chowdary
Department of Physics & Astronomy
Bucknell University



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