Re: Displacement current

to: Richard

An interesting point.  I'm going to run this thru a few really great
research physicists and get their reaction to this magnetic field paradox.
I will report back in a week or so.  One works at Sandia on HV cap projects
and the other works for Maxwell.



-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Sunday, February 28, 1999 2:13 AM
Subject: Displacement current

>Original Poster: Richard Hull <rhull-at-richmond.infi-dot-net>
>Dr Resonance wrote:
>"It's not magic -- it's physics.  A Tesla coil produces "displacement
>currents" in air because the air represents a dielectric while the
>represents a plate of a capacitor.  The second plate is represented by
>isotropic capacitance and plate to ground capacitance of nearby room
>etc.  A displacement current has unique and different properties than
>air to ground currents which produce the wandering spark phenomonea of
>You might read some early Maxwell for good descriptions of displacement
>It is interesting to note that in Maxwell's day he invented the
>displacement current on a whim as a logical and common sense item, even
>though there is absolutely no conductive item in a capacitor's
>dielectric to support the classic current seen in wires and metallic
>conductors.  It also made his equations a full featured set.  This
>current is found in all capacitor dielectrics, according to theory.
>However, in a vacuum dielectric capacitor, it appears to generate no
>magnetic field between the plates!!!!
>This was most troubling to Maxwell and he wrote to several scientifc
>friends that he hoped some proof of exisitance of the vacuum
>displacement current's demanded magnetic field might be found in his
>lifetime.  It was not to be done however.  As recently as 1994 Dr. D.F.
>Bartlett of the Univ of Colorado made the attempt using an ultra
>sensitive SQUID between two plates of a flat plate capacitor in vacuo.
> He found 'zippo' mag field during charge or discharge.  (this is a
>though experiment as the wires to the cap and metallic plate elements
>will create a field as we all know.)  Being a lock step physicist he
>struggled for an explanation in his paper.  Ortherwise all sorts of
>skeletons come out of the closet...(action at a distance, etc)   He went
>into an arcane mathematical diatribe using the now, for the most part,
>disgarded Amperian current force laws to say that the circuit currents
>in their flow and ebb create canceling mag fields via the plates.  (most
>folks cleave only unto the lorentz law which is in direct conflict with
>ampere's old law.)  The Lorentz laws somehow don't generate canceling
>fields....Gee, sure wish they did.
>Maxwell could see logical delema this in his own life time and was
>adverse to using the Amperian current laws as they produce forces not in
>line with his theory.  It vexed him mightily and to his dying day he was
>most concerned about the demanded, but seemingly missing magnetic field
>in the interplate vacuum dielectric.
>So by all means, read up on the displacement current.  It is dished out
>in huge helpings to all us engineers.  Fortunately we don't need to fret
>about mag fields inside our dielectrics so we never "auto-generate" the
>question.  Physicsists, however, are not so lucky.
>While reading up on the THEORY it might be wise to heed the words of
>Sir Frances Bacon from his essay on studies.................
>."Read not to contradict or confute, nor to believe and take for
>granted,  nor to find talk and discourse, but to weigh and consider".
>Richard Hull, TCBOR