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| Veritasium "How Electricity Actually Works" |
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| vad:
--- Quote from: electrodacus on May 11, 2022, 11:42:00 pm --- --- Quote from: vad on May 11, 2022, 11:35:52 pm ---I hope nobody argues here that oscillating EM field does carry energy. Examples are gamma rays, X-rays, UV light, visible light, microwave radiation, radio waves from terahertz to sub-hertz bands all transfer energy. Why is it so hard to realize that a constant EM field also carries energy? --- End quote --- Magnets have a constant magnetic field so do they transfer any energy if sitting next to a copper wire ? --- End quote --- You need both electric and magnetic field: S = E x H S is energy flow in any given point. Energy flow outside a region of space is a surface integral of S over surface of the region. I’m just writing this to forestall desire to add constant E field to your example (e.g. fix the magnet between electrodes of charged capacitor). Surface integral of S would be zero over any arbitrary surface. There would be no energy transfer. |
| T3sl4co1l:
--- Quote from: vad on May 11, 2022, 09:09:54 pm --- --- Quote from: Naej on May 11, 2022, 08:55:27 pm --- First show your solution for a circuit which extract 1% of the energy travelling in the vacuum in the diagram. --- End quote --- Create vacuum in the box and heat the outer wire (cathode) high enough so sufficient number of electrons will flow towards the inner wire (anode) to tap the 1% of energy. They call this a diode vacuum tube, don’t they? Now is your turn. --- End quote --- Careful: an unevenly heated box exhibits free electron drift. A tube diode is a heat engine, albeit a very terrible one. Consider this SPICE model fitted to 1/2 6AL5: it has a negative voltage in it, corresponding to the tail of the thermal energy curve. This tail is exponential, interestingly enough (or, not at all), hence the ideal diode, and the nonlinear dependent source expresses the Child-Langmuir law at higher currents (evidently the cylindrical geometry gives an exponent somewhat lower than 3/2 (inverted as it's solving for voltage, hence 0.775). So, for a 6AL5 that spends about a watt of heater power, you can put its two diodes in parallel, and get a whopping couple of microwatts out. Whereas in an evenly heated box, the space charge will have some drift velocity, much as the electrons in the bulk conductor; it will be hard to extract any meaningful power from it though, as the maximum difference in energy is merely the difference in voltage, of course. Tim |
| vad:
--- Quote from: electrodacus on May 11, 2022, 11:39:20 pm --- Can you be more specific ? --- End quote --- Sure. Charged particle (an electron) gets accelerated in electric field. |
| EEVblog:
--- Quote from: IanB on May 11, 2022, 07:18:57 pm --- --- Quote from: electrodacus on May 11, 2022, 06:55:56 pm ---You have a wrong understanding of what energy is and how it is transferred from source(battery) to load (lamp/resistor). --- End quote --- If on the one side we have electrodacus, who is right, and on the other side we have the rest of the world, who are wrong, then really all rational people would wish to be with the rest of the world and remain wrong. Apparently, in this scenario, being wrong is the right place to be. --- End quote --- The other big thread used to be filled with the Maxwell/Poynting Bro's absolutely shooting down anyone who dared even hinted at suggesting anything other than a 100% Poynting explanation, and heaven forbid if you got even even the slightest direction of Poynting vector wrong, it's was flaming pitchforks. Now all the Poynting bros have vanished and both threads are now completely dominated by the Energy In The Wire (EIT) absolutists. LOL :-DD :popcorn: |
| SiliconWizard:
The truth is out there. |
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