Re: Experiment - Displacement Current's Magnetic Fields

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Paul,

On 12 Mar 2002, at 7:48, Tesla list wrote:

> Original poster: "Paul Nicholson by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <paul-at-abelian.demon.co.uk>
> 
> Hi Terry,
> 
> > I guess one could look at the "invention" of dD/dT as a great
> > theoretical leap, or a kludge to make the darn thing work ;-))
> 
> A fair description.  Picture yourself as a 19th century scientist
> trying to make sense of electricity and magnetism. They are each
> described separately by Coulombs law and Biot-Savart, and you know
> they are somehow connected because you have also have Faraday's and
> Ampere's laws.  You have an 'action-at-a-distance' description of
> gravity and static electricity based on a 'force field', ie the force
> that a test particle experiences (presumably instantly) in response to
> the 'source' of the field.  You desire a similar thing for B too.  You
> know it must be a vector because it has to describe the force on a
> test charge.  And you know that B must somehow satisfy Ampere's law.
> So you invent a B field vector and use it to describe Faraday's law,
> etc, fine. But when you come to look for a mathematical description of
> Ampere's law, you hit a big snag.  You find you cannot get a self-
> consistent mathematical description of this law.  It offers two or
> more different values for the voltage induced in a wire, depending on
> which surface you integrate the field across.  This was the famous
> 19th century crisis in electromagnetism.
> 
> Maxwell was motivated to plug in a dD/dt term because it gave the
> simplest bit of math which described Ampere's law and it still worked
> for the other stuff.  The requirement was a self-consistent description
> of Ampere's law, that's all.  Maxwell will have also noticed that
> putting this term in made the description of Ampere's law identical in
> form to Faraday's law, which was also pretty neat.
> 
> So far so good: the quest for a self-consistent description of the
> existing laws of electromagnetics was successfull.  If that was as
> far as it went, it would be pretty good stuff anyway.  
> 
> But then it gets interesting.  You explore the consequences of the
> mathematical description you have assembled, and you quickly realise
> that they imply some new, hitherto unknown, phenomena: You find that
> sources cannot instantly affect test charges - there's a small time
> delay, and you find that energy can leave the system through a 'wave'
> type variation of the field vectors.
> 
> The vital lesson from this, which says something deep about
> nature:  In striving to ensure the self-consistency of a mathematical
> description of a known physical law, the math unavoidably *predicts*
> a completely new phenomena.  Just as 2+2=4 unavoidably predicts that
> 4+4=8, you find that sources can only affect test charges after a
> small but finite delay, and that a B field can raise an E field (and
> vice versa) in the complete absence of any movable charges.   
> 
> So in one sense, the math descriptions of the laws of physics can be
> regarded simply as compact recipies which work, therefore we use them.
> But, in addition, they provide strong hints of deeper connections in
> nature between apparently unrelated phenomena.  This certainly shook
> the 19th century scientific establishment, who were beginning to 
> think that they had everything sown up.
> 
> This happens all the time now, and we take it for granted. 
> For example, you're a mathematician (Dirac) looking for a self-
> consistent description of electrons, one that is compatible with
> relativity, but the math forces you to use objects called 'spinors'
> rather than scalars or vectors, and these in turn force you to a
> prediction that electrons spin, and that there is an undiscovered
> particle which is the opposite of the electron - the positron.
> 
> As a general rule, we find that if you make up a mathematical 
> description of something that is a) the simplest possible, and b)
> self-consistent, and c) compatible with existing stuff; then as often
> as not, your equations will also *predict* something that you didn't
> know before hand.  You're getting knowledge out of the equations that
> you didn't have to put in.
> 
> We can experience this process personally:  Make up the simplest 
> possible self-consistent description of a TC resonator, using the
> existing elementary laws of electromagnetics.  You don't have to use
> any math or physics beyond what's taught in high school. The resulting
> equations predict a certain voltage profile, and you measure this and
> confirm that your calculations are right.  Then you persue the
> mathematical consequences of your equations and just as 2+2=4 implies
> 6+6=12, so you find that a certain shape of current profile is an
> inevitable consequence.  For example a predicted feature is that the
> current max is raised a little way above the base, and that sometimes
> the effective inductance can be greater than the DC inductance.
> Of course, these aren't new discoveries in physics, but they are new
> to us, and we can experience the fascination of unsuspected features
> of nature being predicted from the requirement of mathematical self-
> consistency of the descriptions of the features we already know about.
> 
> So the measurement of current profiles of certain coils is a nicety,
> to help demonstrate the point, but the outcome will have a certain
> inevitability since you've already validated the voltage profile.
> 
> And of course, nowhere along the way is any 'belief' required. Belief
> is quite a counter-productive thing.  If a belief is true, then it
> can be replaced with a self-consistent, validated, reliable and
> productive description.  If a belief is false, then it simply obscures
> what's really going on and prevents progress.  Reliance on belief is
> nearly always fatal for progress - Malcolm's ruler, quarter-wave wire
> length, Corum's nonsense about 'coherence', use of DC inductance at
> resonance, importance of Q factor in impulsed TCs, the endless
> meaningless debates on 'self-capacitance',  the great and silly
> lumped vs transmission-line saga inspired by another Corum-ism.  The
> list goes on into even crankier beliefs.

I hope a crude and early attempt at modelling the resonator through a 
mechanical analogy is not taken by anyone as a doctrine. As a first 
order description it is probably no worse than any of the other ideas 
listed above. But I have been consistent in saying that I thought the 
helical resonator was to be regarded as a structure with its own 
unique set of properties which none of the models prior to the tssp 
effort could describe in complete detail. 

> Replace all of these beliefs by self-consistent rational descriptions.
> Check that they are valid. Then explore the mathematically inevitable
> consequences and predict new things.  And so on.  Proceed in this
> fashion in order to make up the for the 'lost century' of work in this
> field.  The process ensures that if there's any exciting 23rd century
> physics waiting to be discovered, its discovery will be kind of
> inevitable, we will notice it when it comes because we will have open
> minds, unhampered by preconceived entrenched beliefs, and we will have
> the wits and methodology to investigate, understand, and exploit it.
> --
> Paul Nicholson
> --

Hear hear!

Regards,
Malcolm