Very thoughtful answer ... ... in fact the part about shear strain density seems to have relevance to what I was trying to verbalize wrt the interplay between temperature, electrical conductivity and mechanical strain in a few alloys: especially constantan and similar strain gauge alloys.
Hope this is not reading too much into your comments but the net effect of electrothermal dynamics in a few alloys seems to be what can be called "ghost current" in the sense of the anomalous energy across the alloy being a function of Ohm's law: for instance where (E = .045 volt / R= 5 x 10-6) and the resultant current I = 9,000 amps, yet without the expected physical effects. This is an actual measurement, according to Dotto's patent. IOW - as surprising as it may seem, this exact subject area has relevance to a possible mechanism for enthalpy in a metal hydride devices (perhaps including the Rossi device) when the active material has a negative temperature coefficient of resistance. That is, when one assumes that to avoid conservation of energy problems, there is access to a hidden source of energy (ZPE) based on the precise physical dynamic of the hydride materials at the correct nano-geometry. Maybe I can make this clearer with a bit more contemplation ... Jones From: jwin...@cyllene.uwa.edu.au Subject: Re: [Vo]: Why are the electric and magnetic fields perpendicular? Mark Iverson wrote: Just wanted to throw out a question to the Vort Collective... In an EM wave, why are the electric and magnetic fields perpendicular to each other? The answer to the question is really quite simple and it comes from our definition of what these fields are - which is in turn dictated by what we can measure with instruments. The most fundamental quantity related to these fields that nature seems to possess is a 3 dimensional time varying charge displacement field whose dynamic characteristics are excellently described by Maxwell's equations and whose definition seems most completely given by the two components which are conventionally called the vector and scalar potentials. However to date we are unable measure either of these components directly, but can only measure their differentials - eg the rate of change of scalar potential with distance (= electric field) and the integral around a loop (ie "curl") of the vector potential (= magnetic field). It turns out that when this charge displacement field is propagating in a vacuum, these two components are naturally perpendicular because they are orthogonal components (in a mathematical sense) of the one entity. One might just as well ask "why is length always perpendicular to breadth?". The answer would be simply that it is a convenient way to measure and define two independent components of a useful quantity called "area"! To provide an intuitive illustration of an EM wave one might imagine a long steel rod, one end of which is suddenly given a sharp torsional jerk or twist. This torsional displacement wave is a pure shear wave as there is no compression or rarefaction associated with it, and it will propagate along the rod from one end to the other as a coherent entity and at at characteristic speed determined only by the density of the material and its shear modulus (spring coefficient). If the mass displacement in the material is equated to the charge displacement in the vacuum then (I think!) this becomes a very good analogy of an EM wave propagating in a vacuum. The reason I have chosen torsional waves is because as far as we know the vacuum only supports charge based shear waves (ie displacement perpendicular to propagation. Experiments seem to prove that the vacuum does not support charge based pressure waves - ie displacement parallel to propagation as in sound waves - which is very surprising and remarkable I think!) If we now consider a small volume of the steel rod at its surface and analyze the stresses and strains in that volume, then we can always identify two conjugate quantities that between them support an oscillation and due to their distributed nature support the wave propagation. An analogous quantity to the vector potential (charge proximity times its velocity per unit volume) I think would be the linear momentum density (mass times velocity per unit volume). So the analogous quantity to the magnetic field is the mathematical "curl" of this - which is how much rotational component is present in this momentum. This is very closely related to (and possibly exactly equal to) the *angular* momentum density. The direction of angular momentum is always specified by the axis about which the quantity is revolving - and so in the case of this small volume at the surface of the rod, this axis is perpendicular to the surface of the rod. The analogous quantity to the electric field (or electric displacement) I think would be the shear strain density (ie how much the material is displaced in shear per unit distance along the rod and per unit volume). This shear displacement of course occurs in a direction which is tangential to the surface of the rod and about its axis - that being the direction that we applied the initial jerk. So here we have the magnetic field (angular momentum density) which is perpendicular to the surface of the rod, and the electric field (shear strain density) which is tangential to the surface of the rod, and both of these two are perpendicular to the direction of propagation of the wave along the axis of the rod. Now you can see that these two fields are simply mathematically orthogonal energy components of the single entity which is the wave motion. They are perpendicular only because of the interacting components and their definitions that we have chosen to describe the wave in terms of - in this case "angular momentum" (kinetic energy) and "shear strain" (potential energy) components. If we chose instead to describe an EM wave in terms of its vector potential (*linear* momentum density) and its electric field (shear strain density) then these components would still be mathematically orthogonal but they would be *parallel* in space. (They must always however be perpendicular to the direction of propagation because EM radiation supports axes of polarization.) So the conjugate fields of an EM wave are only perpendicular because we chose to define the kinetic element in rotational units. If instead we chose linear units - such as the more fundamental but less measurable "vector potential" or even the (possibly one-day measurable) "time rate of change of vector potential", then the oscillating fields of an EM wave would be parallel.
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