Talk:Ivor Catt/Archive 10

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Is a Heaviside energy slab travelling between parallel plates "TEM"

I personally at the moment think that it is a TEM wave altho' Im willing to be persuaded otherwise!.--Light current 22:07, 26 February 2006 (UTC)

To paraphrase the infamous CEM Joad, It all depends on what you mean by "TEM", and indeed what you mean by "Heaviside energy slab". If, by the latter, you are referring to the transfer of energy frm (say) a battery into a resistor with the "parallel plates" acting as the connection between the two, and by the former you mean "transverse electromagnetic" in the sense that Maxwell did, the answer to your question is undoubtedly "No". This situation has current flowing in the conductors, and so has a J component; Maxwell's "transverse electromagnetic wave" has J = 0 - it consists only of electric and magnetic fields which are continually changing in such a way as to be self-sustaining. A Heaviside energy slab is certainly electromagnetic, but it does not fit the very specific definition that physicists mean by "transverse electromagnetic wave". Catt's "Theory H" would appear to be Heaviside engaging in a "What if?" exercise in constructing a Poynting Vector type model for energy flow to the case of current flow in a conductor. Heaviside obviously got something sensible out of it, but I very much suspect that he only thought of it as an alternative view of the situation that might possibly yield a useful insight, not (as Catt does) a complete replacement for the "standard" model. -- Kevin Brunt 20:10, 27 February 2006 (UTC)

Kevin, I may be dense, but what do you mean by : the very specific definition that physicists mean by "transverse electromagnetic wave" What is that defn? Also, if it is not a TEM wave flowing down a TL, what is it?--Light current 22:31, 28 February 2006 (UTC)

Consider Maxwell's Equations for the situation where J = 0, (ie no moving charge/no current flow). Very loosely Ampere's Law (as modified by Maxwell) says that the magnetic field is proportional to the first derivative of the electric field and Faraday's Law says that the electric field is proportional to the first derivative of the magnetic field (where the constant of proportionality has a negative sign). It follows that the magnetic field is proportional to (minus) its own second derivative. One function which fits this condition is sin(x). I'm really only drawing an analogy here (I'm ignoring the complications due to the curls), but the point is there; the two differentials and the reversal of sign can make up a sort of "feedback loop" - a sinusoidally-varying magnetic field is self-sustaining, but in order to do so it must move in a direction at right angles to the direction of the field, at a specific velocity, and Faraday's Law requires that there be a sinusoidally-varying electric field, which is oscillating at right angles both to the magnetic field and to the direction of motion. This is the solution that Maxwell saw. At the time his modification of Ampere's Law was informed speculation and his derivation of a transverse wave involving electric and magnetic fields was a prediction that could be passed to the experimental physicists to be tested. -- Kevin Brunt 23:15, 1 March 2006 (UTC)

The differences you seem to be drawing between a guided and unguided waves are that in the one case, current flows in the conductors and in the other case there are no conductors so current cannot flow. Am I correct?. --Light current 01:11, 2 March 2006 (UTC)

I would distinguish between a) a current flowing in a conductor, b) an electromagnetic wave in free space far from a conductor and c) all the possibilities in between, including waveguides. In case a) the electric and magnetic fields are "tightly bound" to the current. When the current "leaves" the conductor, the energy in the fields leaves with it. In case b) the energy is entirely independent of current/motion of charge. In the variants of case c) there is interaction going on. In a waveguide, the electromagnetic fields induce charge motion (current) in the conductor, which creates electric and magnetic fields which, when added to the original fields, create a new "resultant" wave which is a reflection off the surface of the conductor. Various other situations, particularly when the size of the conductor and the "wavelength" corresponding to the rates of change of current and fields are comparable, give rise to "antenna" effects. Nigel's leading edge is a case c), but he is over-emphasising the edge relative to the "DC current" behind it. -- Kevin Brunt 23:15, 1 March 2006 (UTC)

Surely in both cases, the energy can flow as TEM can it not? --Light current 01:11, 2 March 2006 (UTC)

Electromagnetism tends to have everything acting at right angles (cf Fleming's Right Hand rule); "transverse electromagnetic" is read by physicists more precisely as "electromagnetic transverse wave" and the use of "TEM" in situations without oscillation is confusing. The fields associated with a DC current in a conductor are "electromagnetic" but adding "transverse" is misleading. -- Kevin Brunt 23:26, 1 March 2006 (UTC)

I think it is quite sufficient to use the universally accepted definition of TEM waves as:

those em waves that have both the electric and magnetic fields always at right angles to each other and to the direction of propagation.

They can exist between // plates or in a coaxial line.--Light current 01:56, 2 March 2006 (UTC)

There is an implication in the word 'wave' which is close to the heart of Catt's position, and that is that what is at right andgles (and thus "transverse") is not the field, but the oscillation of the field. Catt's "TEM step" has fields at right angles, but they are the fields due to the DC J component, so there is no oscillation, so his "TEM" is not the same thing. (He is also picking those bits of the fields that match his argument; he ignores the fact that the magnetic fields around the conductor is circular (cylindrical) and that with the voltage front advancing at a velocity less than that of light there is a longitudinal component to the electric field propagating ahead of the step.) This is one of the key points to understanding Catt's ideas and ought to be represented on the main page. -- Kevin Brunt 13:07, 2 March 2006 (UTC)

Also in a guided wave, coax, // plates etc, currents are only assumed to flow in them. Actually RF mag fields nd therfore currents cannot penetrate a perfect conductor, hence the current tends to flow at the surface of the conductor instead (skin effect). Therfore in the li=mit, a guided wave travels in basically the same manner as an unguided wave. I am in error somewhere?--Light current 23:52, 28 February 2006 (UTC)

See above. You need to consider the two limits; DC, where the fields are firmly attached to the conductor, and HF, where the fields are only being guided by interaction with the surface of the conductor, and are quitely likely to carry on in a straight line instead of following the conductor round a curve. -- Kevin Brunt 23:26, 1 March 2006 (UTC)

The 'wavefront' question

Catt and Walton have different views on this. By email in 2000, Catt stated it was a shame that "TEM wave" had disappeared from textbooks, then Walton (Catt's co-author of some articles and a book in 1979) stated he didn't believe electricity is a TEM wave, because there is no wave in a computer logic step! It is just a constant voltage pulse. (However, there is a variation at the front, which is vital to the Catt anomaly/question.) Heaviside's own view of 1893 in "Electrical Theory vol. 1" is entirely consistent with my point of view and with modern quantum electrodynamics: the step is driven forward because of radiation. Heaviside said of conventional theory (current causing field): "We reverse this; the current in the wire is set up by the energy transmitted through the medium around it ..." Nigel 172.201.199.96 11:24, 28 February 2006 (UTC)

You say the step is driven forward because of radiation. What is a TEM wave if not radiation?--Light current 23:55, 28 February 2006 (UTC)

You seem to be thinking of the the steady part of the TEM wave where the voltage is constant [1], but not for the front electron where the voltage step is rising and where the Catt problem lies. Whenever charge accelerates, it emits electromagnetic radiation transversely, and this happens in the rise portion of the front of the TEM wave. Where the voltage is steady at 10 volts, the electrons can be treated as drifting at a steady pace. In the rising portion, transverse radiation is crucially important, but where the voltage is steady the longitudinal push (parallel to the conductors) comes into play. Nigel 172.201.86.143 11:58, 1 March 2006 (UTC)

Can charge carriers accelerate this fast? Or are you talking about 'abstract charge' that needs no carriers? I think you must be. This abstract charge, though, is part and parcel of the electromagnetic wave - nothing to do with conductors. If it was then em radiation could not flow in vacuo. Surely all your convoluted explanation can be replaced by considering the step as an range of sinusoidal frequencies extending to infinity and then applying Maxwells eequations to each component separately. There is no need to treat the step (or ramp if you like) as some sort of magical, mysical entity that defies normal analysis- its not. The only thing that exists at the wave front (and behind actually) is em energy travelling along the line. End of story.--Light current 02:09, 2 March 2006 (UTC)

Accelerate what fast? The time taken for the charge carriers to accelerate from a net drift of zero to the final average drift speed of 1 millimetre per second or so for a typical 1 Amp current is the rise time of the TEM/Heaviside step. That is not zero. This point is also made quite clearly by Dr Ian Hickman in his article "The Catt Anomaly" (Electronics World, Oct 04, p 38): "the notional displacement current only flows where the electric field strength (voltage gradient) is changing. ... So the displacement current of 1 A flows only at the point where the wavefront is. This implies that if the voltage step is instantaneous ... the displacement current is therefore infinite. [displacement current is proportional to dv/dt ~ v/0 = infinity]. This is a major difficulty ..." I differ with Hickman over the solution. Hickman says it means displacement current is simply wrong and should be "consigned to history", but the reality is that no real step has zero rise time, so you aren't dividing the voltage increase by zero time and getting infinity.

Electromagnetic energy emission by accelerating charge isn't "some sort of magical, mysical entity that defies normal analysis".

"The only thing that exists at the wave front (and behind actually) is em energy travelling along the line." - this statement is wrong because the em energy is controlled by the two conductors, and if you stop the current flow in one conductor the other conductor is affected, which proves the transverse (energy exchange) mechanism at the front of the pulse is real. Nigel 172.214.15.225 12:03, 7 March 2006 (UTC)

---

TEM continued

If Heaviside's model yielded results that were consistent were the observed facts, it will yield results that are consistent with other models that fit the same facts. What scientists then do is to think up situations in which the completing models yield different results, and do the experiment to find out which comes up with the right answer. The fact that a model gives the right answer does not mean that the model itself is correct. It is unclear exactly what Heaviside was envisaging as a model for charge when he announced that "We reverse this". It is quite possible that he deliberately avoided making a decision and was waiting to see what would turn up. What did turn up was the electron. Catt complains that Heaviside's energy current fell out of favour because of "wireless"; it would surely be more correct to say that it was the electron that ousted it. Modern theory has the electrons interacting with each other by way of their fields; this is neither "Theory N" nor "Theory H", but both simultaneously. -- Kevin Brunt 20:33, 28 February 2006 (UTC)

Also, did Heaviside actually describe his energy slab as "TEM", or is it just an interpolation due to Catt? It springs up in the first chapter of Catt's "Electromagnetism" as an assertion that a voltage step is a "TEM wave". He provides no definition of what he means by it at all. It is this, rather than anything to do with displacement current or Maxwell's Equations or anything else, that is the root of the Cat Anomaly. Catt is using physics terminology to mean something different. McEwan was aware of this and provided an explanation of what Catt thought that his Question meant. Pepper, not being a read of Wireless World, attempted to answer the Question according to the commonly-accepted meaning of the words and came up with an entirely different picture. It is clear that Catt does not understand his Question - the correct answer is probably "pedwar deg dau" (which is "zweiundvierzig" in Welsh - I have no doubt that Catt would object to compulsory Welsh lessons in schools in Wales....) -- Kevin Brunt 20:33, 28 February 2006 (UTC)

Kevin, Heaviside never used the term "TEM wave" and Dr Dave Walton disapproves of it because a wave is defined as a periodic variation in something. Catt alone prefers the term "TEM wave" but ironically refuses to consider it as being transverse in nature. Heaviside referred twice to "a slab of energy current" in his writings. Heaviside also (independently of Poynting), discovered the Heaviside-Poynting vector for electromagnetic radiation, which does say that both the electric and the magnetic field vectors are orthagonal to the net energy flow. However, Heaviside understood that for transverse radiation including light, there is energy moving transversely (along electromagnetic field lines) as well as in the direction of propagation, which is the whole point of a transverse wave as compared to a longitudinal wave. This is the key to the whole business, the modern ignorance of the fact that a transverse wave is a wave with a periodic transverse variation. Catt clearly doesn't understand waves at all, or he wouldn't choose to apply the term to direct current.

Once again, see [2]: at the front of the logic step, electrons are accelerated where the voltage is rising. Whenever charge accelerates, it emits electromagnetic radiation transversely, which happens in the rise portion of the front of the TEM wave. Transverse radiation is important at the front of the logic step, which the Catt anomaly deals with, although where the voltage is steady the important energy flow of electricity is longitudinal. Nigel 172.201.86.143 11:58, 1 March 2006 (UTC)

Would Nigel say that this radiation travelling normally to the plates from one plate to the other is what causes the charge separation in the line or capacitor? Also would Nigel say how the energy having started out in a battery comes to be evenly distributed in a charged capacitor or line if the energy cannot actually flow down the line to distribute iself?--Light current 15:29, 1 March 2006 (UTC)

If you look at the full facts: the electromagnetic energy pulse is controlled by the charge in both conductors in an interdependent way. If you cut off one conductor, the charging of the other one is immediately affected. Because the pulse is going at light speed but electron drift is very small, the pulse is continuously overtaking the electrons as they are accelerated. The physics is further complicated by the problem that in the Catt anomaly diagrams, Catt shows a current flowing in the conductors where the potential along the conductor is constant 10 volts. No electric current will actually flow under this condition, because you have to have the electric field varying with distance along a conductor to cause electron drift. (The electrons accelerated briefly at the front will presumably soon slow down behind the front due to resistance, so "energy current" not "electric current" is possible where the voltage is constant with distance along a conductor.) Catt of course fiddles it completely by drawing displacement current as flowing where the electric field is both constant with time and constant with respect to distance along the transmission line. The Catt Anomaly is an total, complete, and utter hoax from start to finish. Nigel 172.213.66.114 14:19, 9 March 2006 (UTC)

Nigel has a major problem with his accelerating charge argument, because when you "map" it onto the motion of the electrons, the "acceleration of charge at the voltage step" becomes the acceleration of the electrons from rest to the electron drift velocity. Since the "at rest" state is actually "equal motion in all directions", and the conduction electrons are "bouncing" off the nuclei, etc, Nigel needs to be able to explain why the acceleration due to current flow radiates, while the much larger accellerations and decelerations due to the thermal motion don't radiate! -- Kevin Brunt 23:32, 3 March 2006 (UTC)

Good points! Well said. Im not sure if Nigels direction of radiation is correct either yet. I havent worked it out. Is is Larmours formula?--Light current 23:39, 3 March 2006 (UTC)

Kevin, accelerating charge radiates electromagnetic energy in a direction at right angles to the direction of the acceleration. Normal accelerations due to thermal motion of electrons occur simply a result of collisions, and the radiation is called heat. This applies to all conduction zone electrons. The nature of the electric field in electricity causes a more gradual acceleration and a lower frequency energy emission. Infra red radiation is of higher frequency than microwaves. Nigel 172.214.15.225 12:26, 7 March 2006 (UTC)

Nigel asserts that Catt and I show that most (nearly 100%) of the energy transfer in electricity is energy of "radiation" or "electromagnetic field". I think that Nigel is referring to a) Catt's demonstration that a pulse travelling along a TL has equal amounts of energy in the electric and magnetic fields, and b) Nigel's own calculations to show that the kinetic energy of the electrons moving at the electron drift velocity is far too small to be relevant. Now the problem with a) is that it only establishes a relationship between the inductance and the capacitance of the TL that explains the propagation velocity. It doesn't of itself combine the fields to make them "electromagnetic" or "radiation". As for the kinetic energy of the electrons, nobody is arguing that it is significant in the first place. Nigel's computations in Electronics World wildly over-estimate the mass of the electrons in motion. The smallest figure of his that I recall was a good 100 times too large. The KE is so small that it can be ignored. It also is a "one-off" input of energy as the electrons are brought up to speed. By my reckoning the KE is the only energy available for Nigel's "radiation" due to the accelerating charge. -- Kevin Brunt 23:32, 3 March 2006 (UTC)

Kevin, I state I deliberately exaggerate the mass to err on the side of caution because it depends on the atomic number and composition of the conductor in question. Dr McEwan claimed that electricity is due to electrons physically "nudging" one another along, like a line of ball bearings. If everyone agreed that this longitudinal wave model was false, then everyone would have to admit that electricity is electromagnetic energy carried along transmission lines, and that the fluid analogy of electric current does not carry the energy. Instead, all the textbooks start out wrong-footed with the picture of electricity as a current of electrons, not an electromagnetic field. Once you accept that the electromagnetic field is the primitive which drives the electron drift current, then you have to face the issue as to whether it is purely longitudinal or has a transverse component. It does have a transverse component where the current is rising (in the forward-moving section of the transmission line where the voltage varies between 0 and its peak of v volts). Since we know that the electrons are accelerating in this portion, we know they emit transverse radiation, so the conductors transmit energy to one another, enabling the logic step to propagate guided by both of the conductors. This is self-evident. As to why the electrons accelerate in the first place when you connect the transmission line to the battery, it may well be a longitudinal push. But as soon as the transverse exchange of energy between the two conductors is set up at the rising portion of the logic "step", each conductor causes the current flow in the other. Nigel 172.214.15.225 12:26, 7 March 2006 (UTC)

Nigel, the problem with your kinetic energy exercise is that it doesn't correspond to the "line of ball bearings" description. Your model describes the motion of isolated independently-moving electrons; the "ball-bearing" model considers the conduction electrons as behaving as a rigid mass which transmits force along the conductor. The crux lies in your statement that "all the textbooks start out..."; the "ball-bearing" model is part of the description used at an introductory level. As for moving electrons versus electromagnetic fields, while Heaviside said "We reverse this", someone a good deal more famous said "Nevertheless, they move." And the electrons do move - it is not possible to explain the electrochemical effects of an electric current otherwise. Heaviside's "energy current" is merely an attempt to look at the issue from a different viewpoint; "Theory N" and "Theory H" are not incompatible alternatives, but are parts of the same whole. Without the electric and magnetic fields you can't understand capacitance and inductance, but without the charge/current flow in the conductor, you lose resistance and the electrochemistry. Since capacitance and inductance are both "AC" properties, it is not surprising that textbooks start with current. -- Kevin Brunt 18:58, 7 March 2006 (UTC)

Kevin why do you say "the problem ... is that it doesn't correspond to the "line of ball bearings" description."? I don't care about the false model. I want the facts. It is a benefit that the facts don't correspond to the false earlier model. The electrons move due to the field. You next state this as if I disagree with it. Then you start talking about electromagnetic fields as if you are trying to sell me the model I've just described. Your response reminds me of the argument: ‘(1). The idea is nonsense. (2). Somebody thought of it before you did. (3). We believed it all the time.’ - Professor R.A. Lyttleton's summary of inexcusable censorship (quoted by Sir Fred Hoyle in ‘Home is Where the Wind Blows’ Oxford University Press, 1997, p154). Nigel 172.189.107.149 12:39, 8 March 2006 (UTC)

It is Catt's "Theory C", which denies the existence of current that has problems. Without charge and current, it can't explain resistance and so has no way of explaining Ohm's Law. -- Kevin Brunt 18:58, 7 March 2006 (UTC)

Catt experimentally and theoretically shows that any charge of "static" electricity is identical to an equilibrium system with equal energy currents flowing in opposite directions. In this case, there is no net electron drift current, hence no resistance or magnetic field, but there is still energy current, travelling at light speed in both directions, each current being described by the Poynting vector. The reason why there is no electron drift current (and heat dissipation by resistance) is that there is no gradient in the electric field with distance. The reason why there is no magnetic field is that the magnetic field curls cancel each other out. All you have is the electric field. This is a very brilliant model which should be key to the Catt theory. If you theoretically cut up such a charged capacitor until you get a pair of charges, you immediately have charges as trapped Heaviside energy current, going around in a little loop (hence spin), producing a radial spherically symmetric electric field as seen at long distances and a magnetic dipole from the way the magnetic field lines add up. (This is consistent with the standard model, in which the mass of every fundamental particle comes from an interaction of a charge with the surrounding Higgs field of the vacuum.) It does annoy me that Catt won't correct errors in his books, but he does not universally dismiss electric current. Catt uses "static" charge in capacitors to show how you don't have to have an electric current to have energy current. Nigel 172.189.107.149 12:39, 8 March 2006 (UTC)

I think that we need to get away from the twin parallel conductor transmission line for a bit. It's all very well trying to invoke symmetry, but the propagation arguments apply perfectly well to a single conductor in empty space, when it should be perfectly obvious that there is a changing electric field propagating longitudinally ahead of the voltage step. What is happening is that the electrons are moving relative to each other- their spacing is changing, which requires an input of energy - there is longitudinal "displacement current" associated with the charging of the capacitance of the conductor, but because there is no second conductor, there can be no interchange of energry with it. The "between the conductors" part of the story is an optional extra! -- Kevin Brunt 18:58, 7 March 2006 (UTC)

The single conductor is the monopole radio aerial situation. The self-inductance for a single conductor is infinite, and it radiates electromagnetic radiation energy transversely. If you place another radio aerial parallel and feed it with a current which is the inverse of the current fed into the first aerial, the radio-type electromagnetic radiation emitted transversely from each aerial will exactly cancel out to zero field strength as seen at a large distance (several times the distance of the separation between the two aerials). So this is the way to analyse the two conductor transmission line. Each conductor swaps energy with the other, creating the transverse electromagnetic wave which creates the current in the other conductor. Nigel 172.189.107.149 12:39, 8 March 2006 (UTC)

Basically, the TL in Catt's writing is merely obfuscation - the westerly/southerly dichotomy is not a fundamental issue of physics, but merely a detail of the particular situation, where Catt is playing up the perpendicular component and ignoring the bits that don't fit his story. -- Kevin Brunt 18:58, 7 March 2006 (UTC)

Catt is trying to serve the obfuscating modern physicists a taste of their own medicine. It fails because if someone copies the arrogance of a famous personality, that does not convey fame. It's a bit like Feynman's "cargo cult science", see [3]:

"In the South Seas there is a cargo cult of people. During the war they saw airplanes land with lots of good materials, and they want the same thing to happen now. So they've arranged to make things like runways, to put fires along the sides of the runways, to make a wooden hut for a man to sit in, with two wooden pieces on his head like headphones and bars of bamboo sticking out like antennas - he's the controller - and they wait for the airplanes to land. They're doing everything right. The form is perfect. It looks exactly the way it looked before. But it doesn't work. No airplanes land. So I call these things cargo cult science, because they follow all the apparent precepts and forms of scientific investigation, but they're missing something essential, because the planes don't land.

"Now it behooves me, of course, to tell you what they're missing. But it would be just about as difficult to explain to the South Sea Islanders how they have to arrange things so that they get some wealth in their system. It is not something simple like telling them how to improve the shapes of the earphones." Nigel 172.189.107.149 12:39, 8 March 2006 (UTC)

Nigel, you have not answered my initial point, which is whether your "kinetic energy assertion" is your claimed proof that the energy transfer is by "radiation". -- Kevin Brunt 18:47, 8 March 2006 (UTC)

Kevin, I'm dealing with facts, so I'm not concerned whether McEwan's proof (which is wrong) is based on springs between ball bearings, or indeed elastic strings causing energy transfer, or whatever. The sort of calculation I gave is designed to illustrate that McEwan's model is inconsistent with the amount of energy being transferred. Nigel 172.213.66.114 15:29, 9 March 2006 (UTC)

{Responding to Nigel} The real "fact" is that "McEwan's proof" (which is actually only a simplified, non-mathematical description) derives from basic theoretical mechanics, in which forces are transmitted instantly. Energy is transfered instantly from source to load, and the kinetic energy of the moving electrons is irrelevant - it simply does not appear in the calculations. Yes, it is not a complete model, but it corresponds with the approximations that underlie Kirchoff's current law, and can actually explain Kirchoff's voltage law (ie that the voltages sum around the circuit) as a consequence of Netwon's Third Law. The place where the model diverges from reality is in the assumption that the moving mass is "rigid"; in fact the mass "distorts" under the application of force, and it is in this "distortion" that the explanation of AC effects (inductance, capacitance, etc) lie. Nigel's claim about the kinetic energy is a "strawman" argument - he says it is important, but has not demonstrated that it is so -- Kevin Brunt 16:48, 9 March 2006 (UTC)

The flaw in Nigel's "proof" that the "ball-bearing" model is wrong because there isn't enough kinetic energy is trivially simple; if he had ever worked through the basic theoretic mechanics exercise needed to understand the model, he would have found that the kinetic energy of the moving mass is irrelevant. There is an initial input of KE to bring the electrons "up to speed", but once a constant current (implying constant velocity) is reached, a constant KE is also achieved. What is needed, and what Nigel did not even look for is an explanation of how the energy being delivered into the load and into the resistance of the conductor is replaced from the source. The correct model has the motion of the electrons describing current, and the forces acting to cause the motion as voltages. -- Kevin Brunt 23:11, 8 March 2006 (UTC)

Kevin, fine. But I'm more concerned at present with how the electric current flows in that portion of the conductor behind the front of the logic step, where the voltage is 10 volts. If you don't have a gradient in voltage, there is no way the electric field will make electrons drift one way. The answer seems to be that the electric current in the part of the conductor behind the front of the step, and where the potential is a steady 10 volts, is caused by the magnetic field from charge moving in the opposite conductor. The acceleration of electrons at the front of the logic step is due to the variation in the potential of the electric field from 0 to 10 volts. Once the front has passed the electron by at light speed, the magnetic field created by the motion of the electrons causes the motion of charge in the other conductor, and vice-versa. Nigel 172.213.66.114 18:24, 9 March 2006 (UTC)