Electromagnetic Theory's unfortunate history.
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The Historical background of "The
Catt Question" Ivor Catt, 21 July 2009 |
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The present failure to grasp "The Catt Question" has causes going back a long way, starting with Faraday's Law of Induction, and even earlier, with Oersted's discovery that electric current caused a magnetic field. However, the truth about Oersted's case is more complex and difficult to discuss than Faraday's. So we will keep to Faraday. Faraday's conclusion was that changing magnetic field, or flux, caused an electric voltage and thence electric current. However, let us look at the simplest discussion of his experiment and discovery. We will discuss the one turn transformer. (Also discussed via here at here. ) In the diagram, it is electromagnetic field, not magnetic field, which is delivered into the primary of the one turn transformer. (Caveat.) The way in which such a field can build up, leading to the wrong impression that the primary contains magnetic field, not electromagnetic field, is shown for a capacitor in the graph in my article "Displacement Current" at Figure 3. (See "The Field in a Charged Capacitor".) Whether the primary in the diagram has a single turn or more turns, the scenario is as in Figure 3.. The apparently steady voltage in a capacitor following the exponential rise in that case is in fact composed of energy current, or TEM Wave, or electromagnetic field reciprocating from end to end of the capacitor. The associated magnetic fields cancel out for the purpose of measurement. This is discussed here. The behaviour of a transformer is similar, except that at each end of the transformer there is a short. The incident signal is reversed when it reflects, so that an opposite voltage returns along the transformer. The two voltages being equal and opposite, our voltage measuring instrument registers zero volts. This leads us to think that all that exists in a transformer is a magnetic field, whereas in fact there is an electromagnetic field reciprocating from end to end at the speed of light. This contains electric field as well as magnetic field. (Since the permeability of the material in a transformer is large, this velocity is much slower than in vacuo.) Now in due course, at a later time than that illustrated in the diagram , some energy current exits from the secondary of the one turn transformer and advances towards the voltmeter. However, this is not voltage. It is energy current, TEM Wave, or electromagnetic field as described in Figures 4 and 5 . Thus, the incident electromagnetic field, or TEM Wave, into the primary "caused" a TEM wave in the secondary and "caused" a TEM Wave to exit from the secondary. All was TEM Wave. Electric current did not cause magnetic field, and magnetic field did not cause electric current. More accurately, TEM Wave in the primary did not "cause" TEM Wave in the secondary. Merely, some of the TEM Wave entering the primary leaked into the secondary, in the manner discussed in my 1967 IEEE article, In my article, the energy current transferring to the secondary was called "crosstalk". My book on the www deals with this material. See page 31, page 34 and page 36. Another book of mine covers the same material at page 55. This next paragraph will be very difficult to understand, particularly if the reader does not have access to the photographs, Figures 35 and 36 from my 1967 article. The fact that energy enters the secondary even though there is a short at the front of the secondary is proven in the photographs called Figures 35 and 36. The secondary contains two TEM Waves of opposite voltage polarity, thus initially deceiving our oscilloscope probe, which senses voltage, into thinking there is nothing there in the secondary. However, further down the line the two separate out and our oscilloscope probe sees that there is indeed energy in the secondary, which in due course exits from the one turn transformer and approaches the voltmeter to the right in the diagram . Now "The Catt Question" is actually stated correctly from this point of view. It does not begin; "Traditionally. when a TEM voltage step .... travels through a vacuum from left to right, .... " but rather more correctly it begins with; "Traditionally. when a TEM step (i.e. logic transition from low to high) .... travels through a vacuum from left to right, .... ". It leaves open the fact that the step is magnetic as well as electric. To all those traditionalists (which means in this case more or less everyone) who believe that there exist two kinds of field, electric and magnetic, rather the only the single kind of field, the electromagnetic field, I would here point out that in the diagram, both electric field and also magnetic field are delivered from the battery (at the speed of light) as constituents of the TEM Wave. Thus, magnetism already existed at the moment the TEM step entered the left hand end of the "transformer" primary. But electric field already began to appear in the "primary", and with it electric current. Thus, it was not magnetic field which created, or caused, electric current. Electric current had been there from the start in the primary, switching over to the secondary following my theory/discussion of "crosstalk" in 1967, cited above. The incident signal from the battery contained both electric field and magnetic field, or, more correctly from my point of view, it contained both an electric dimension and a magnetic dimension in a TEM signal. Some of this transferred to the secondary - both the electric and the magnetic dimension, because they are inseperable. Thus, the electric current did not create the magnetic field, and the magnetic field did not then create an electric field and current. Both electricity and magnetism coexisted at every stage, as the two dimensions of a TEM Wave. Illustrative animations are here, specifically at here and here. To see how electric voltage appears to disappear when the TEM Wave reflects at one or other end of a transformer, go to here. Please wait a long time for these animations to download. Only a short pulse is shown, but in reality the TEM Wave fills the whole length, travelling through itself in both directions, and so giving the illusion that there is no voltage. Now causality, supposedly discovered by Oersted's discovery of the deflecting compass needle and later by Faraday's experiment supposedly leading to electromagnetic induction, led to the idea that in a TEM Wave, changing electric field caused magnetic field, and changing magnetic field caused electric field. This idea, frequently propounded, was for instance propounded by Einstein; "Einstein teaches 'The Rolling Wave'. - Albert Einstein and Leopold Infeld, 'The Evolution of Physics', pub. CUP 1938, p154; ' .... What kind of changes are now spreading in the case of an electromagnetic wave? Just the changes of an electromagnetic field! Every change of an electric field produces a magnetic field; every change of this magnetic field produces an electric field; every change of ...., and so on. As field represents energy, all these changes spreading out in space, with a definite velocity, produce a wave. The electric and magnetic lines of force always lie, as deduced from the theory, on planes perpendicular to the direction of propagation. The wave produced is, therefore, transverse.'" Now Einstein's statement above was already in some trouble when he wrote it. It applies most clearly to monochromatic light. In that case, if we do not look too closely at the relative phases of E and H, it is plaubisle to say that changing E field causes H field, and changing H field causes E field. The trouble begins when we observe that sunlight is an electromagnetic wave, because white sunl;ight is not monochromatic. In the case of white light, the rising E field involved in one frequency component (violet) must cause the relevant H field while at the same time the falling E field involved in another frequency (red) must be causing an H field of the opposite sign. Thhuse, superposition has to be assumed even as far as causality is concerned. One might imagine, as an illustration, two men pushing a large weight in opposite directions at the same time, and the weight travelling in both directions at the same time in some way. Superposition can clearly not be applied in such a case. The problem for Einstein's "changing E causes H and changing H causes E" becomes even worse when we move from sunlight to addressing a logic gate switching from felse (0v) to true (5v). If the logic gate remains at "true" for some time, then a steady TEM step travels from that gate to the next. During the "true" period, E does not change and H does not change. How on earth can H be caused by a changing E when E is not changing? Thus, "The Rolling Wave" has a long and illustrious pedigree. It hopelessly confuses "The Catt Question" . From my point of view, only electroagnetic field, travelling at the speed of light, 300,000, can exist. It contains "an electric field dimension" and "a magnetic field dimension". They are in fixed proportion, 377. However, if a TEM Wave passes through a region with other material in it, the TEM Wave can appear to slow down, and the aspect ratio, 377, can appear to change. This is because 300,000 and 377 are based on what we call the "permittivity" and "permeability" of the medium through which it is passing. However, even then, "electric field" and "magnetic field" do not create each other, any more than the width of a passing brick (travelling at constant velocity on its way to the shop window) can "create", or "cause", its height, or vice versa. The truth is that no causality was discovered by Oersted or Faraday. @@@@@@@@@@@@@ A crucial aid to understanding the above was some software by my co-author Mike Gibson. It can be reached via my book at "Mike Gibson's computer Simulation of Inductor and Transformer as transmission line", which went to my page, which discussed what his software did. |
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