In this patent
https://patents.google.com/patent/US787412A/en Tesla proposes to transmit energy at a distance through the earth.
The principle:
Tesla represents the earth as a perfect conductor serving as a reservoir of electrical charges. The idea is to "shake" the earth's electrons around the device by a back-and-forth effect of the electrons between the earth and a capacitor, thanks to a very high voltage resonant device with a terminal capacitor at the top. The action on the earth electrons is not only through the earth connection, but through the remote influence of the capacitor.
A wave will propagate through the earth from this agitation. Precautions are taken to avoid hertzian waves. The resonance frequency is chosen to obtain a standing wave through the earth, that is to say that the earth diameter must be an odd multiple of the quarter wave.
The looping of this wave towards his device, in order to obtain a stationary wave, is supposed to be done at the surface of the earth, at the extravagant speed of 471240 km/s, estimated value for which he gives no explanation, not more than on the lowest usable frequency, for him 6 Hz thus not odd multiple of the earth diameter but equivalent to a half-wave around the earth at the speed he provided.
A tuned receiver, somewhere on earth, would thus recover a part of the emitted energy, differently and more or less efficiently depending on whether it would be an integral part of a node of the standing wave system or whether it would only take a sample of it.
Analysis:
The earth is an enormous reservoir of charges. But the back and forth of charges between the earth and the capacitor does not involve more charges than the capacitor can hold. So there is a huge imbalance between the amount of charges in the earth, and the amount of charges in the capacity. Only a very small amount of earth charges will be affected, which the very high voltages used cannot compensate.
This quantity of oscillating charges will represent a current through the earth. The fact that the earth is seen as a capacitance does not cancel out its electrical resistance, so huge losses are to be expected, which will dissipate the energy over short distances compared to the diameter of the earth. Let's not even talk about the skin effect.
The looping of the wave by its propagation on the surface of the earth is also doubtful, the electrons on the surface of the earth being also subject to resistance. On the other hand, it is surprising that the wavelength chosen by Tesla depends only on the diameter of the earth, while to be stationary while being looped, it is an even multiple of the diameter + half-circumference that should be chosen, taking into account the speed of propagation in each mode.
Effects in real life:
At short distance, it is sure that the device works. A current in the earth can be intercepted with a resonant system in the same way as it is produced. This resonant system will be all the more efficient as there will be a near field coupling between the two terminal capacitances, the transmitter and the receiver.
The device agitates the earth charges only on a very limited area around the system foot. At long distances the ohmic losses dissipate the current and therefore the movement of the charges. To move charges further, a much higher tower would be needed, influencing more distant charges. At distances of tens or hundreds of times the height of the resonant system, the coupling will be drastically reduced, no efficient transmission of energy is possible, especially around the earth, unless you have a tower of non-negligible height compared to the dimensions of the earth, that is to say thousands of km high.
Artifacts:
I see at least two, the Hertzian waves and the issue of power lines feeding the device.
A Tesla coil is a very bad radio antenna, but nevertheless it is one. It radiates electromagnetic waves. When the powers involved are enormous, which is the case, it is impossible to eliminate them totally and low energy signals can be transmitted at great distance.
Finally, it is certain that, without extreme precaution, a non-negligible part of the oscillating electrical energy is re-injected into the electrical lines feeding such a system, either directly through the components of the device by capacitive or inductive effect, or by bad filtering, or by the coupling of these lines with the resonant system. This system influencing the earth charges around it, also influences those of the electric lines around it, and even better because allowing a better coupling. These long lines then act as transmission lines with respect to the earth (common mode), being able to propagate the oscillating current to tens of Km and radiate it in hertzian.
This explains all the facts around the principle. It is understandable that the oscillating energy of such systems can be recovered at short distance, detected at longer distance, but unable to transmit significant energy at very long distance, hence the failure of Tesla to demonstrate his system. It was an unconvincing draft of his future patent 1 119 732 not more convincing.
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Topic: Claims without evidence and off topic answers (Read 4480 times)
