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"Veritasium" (YT) - "The Big Misconception About Electricity" ?
bsfeechannel:
--- Quote from: Uttamattamakin on January 01, 2022, 06:24:56 pm ---Thanks I am the one who made this video. I would sum it up like what you said and add only this. In a classical point of view of physics things happen or they do not happen, in a QFT point of view there are non zero and tiny probabilities of everything happening. Quantum Electro Dynamics is the specific theory that applies to E and M.
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I like your video very much, especially that part where you say that, in QFT, there's no distinction between particles and fields. But I have a question. What if your wire, besides the interacting electrons you showed, also had protons?
--- Quote ---As this video from PBS space time explains much better than me with my barely functional white boards.
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Cool, so the energy-carrying particles are the photons, which are just oscillations in the EM field.
bdunham7:
--- Quote from: SiliconWizard on January 01, 2022, 07:15:41 pm ---you must be following pretty recent advances in physics research...while giving some quantum properties to molecules so far, it still doesn't say that water molecules through a pipe would flow in any similar way electrons "flow".
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No, the concept of the localization of the wave function of any particle or object, quantified as its de Broglie wavelength, has been taught in introductory QM for decades and I had to demonstrate it experimentally (for electrons) in one of my undergraduate physics labs via the standard Davisson-Germer experiment. Nothing new, except that the de Broglie wavelength for larger objects is so small and thus the distribution probability so localized that it is much more difficult to observe.
I did not say that the flow of water through a pipe was in any way 'similar' to the flow of electrons in a wire--nor did I say they were dissimilar-- I simply said that they were both valid concepts.
--- Quote ---Well yes! But we still haven't defined while "through the wire" exactly meant, unless I missed it. Can we find a definition?
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Well, if you want a QM definition, I think it would simply be that the spatial probability distribution of the electrons in question at each point in time ( Ψ [x,y,z] (t) ) mostly falls somewhere within the dimensions of the wire. IIRC, the de Broglie wavelength λ of an unbound electron within a copper conductor is less than a nanometer, λ for a water molecule would be in the femtometer range. The 'odds' of a water molecule tunneling out of its pipe into free space is so low that we don't expect to ever observe it. The electron may have a better chance, but it is still vastly more likely to be found within the wire.
bdunham7:
--- Quote from: rfeecs on January 01, 2022, 06:17:21 pm ---The Poynting vector seems to work for all cases. So why use two different definitions of energy flux?
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Because a simple (and completely solved) problem like my thermal socks unnecessarily becomes a non-intuitive unworkable mess. The real question for me is why you would analyze any problem from the perspective of 'energy flux'. If there's a valid reason to do so, perhaps Poynting is the way to go. There's a reason the Poynting's Theorem and the concept of the S-field shows up where it does.
rfeecs:
--- Quote from: bdunham7 on January 01, 2022, 07:57:32 pm ---
--- Quote from: rfeecs on January 01, 2022, 06:17:21 pm ---The Poynting vector seems to work for all cases. So why use two different definitions of energy flux?
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Because a simple (and completely solved) problem like my thermal socks unnecessarily becomes a non-intuitive unworkable mess. The real question for me is why you would analyze any problem from the perspective of 'energy flux'. If there's a valid reason to do so, perhaps Poynting is the way to go. There's a reason the Poynting's Theorem and the concept of the S-field shows up where it does.
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I agree. If you are analyzing an antenna you would probably use Poynting's Theorem (or your computer would). But for DC, then P = VI works fine. Use the right tool for the job.
Yet people can't agree that energy is outside the wire in the fields vs inside carried by electrons.
There is even talk of electrons in the battery "influencing" electrons in the lamp, maybe by the exchange of virtual particles. Definitely not the right tool for the job.
bdunham7:
--- Quote from: rfeecs on January 01, 2022, 08:45:51 pm ---Yet people can't agree that energy is outside the wire in the fields vs inside carried by electrons.
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IMO, the question is wrong. What is 'the energy'? The energy of what? A charge has potential energy if there is an electric field so that work can be done on it if it is allowed to move from a higher potential to a lower one. The transfer of energy (flow) is in my view the delivery of such a charge to the load. See my Millikan tongs example on the previous page if you haven't already. Whether the energy is 'contained' in the charge or the field seems a questionable question since both are required. You can have any field you want, but without a charge to work on there's no energy. Likewise, the electron itself doesn't contain energy simply by its presence (well it does, but that is a different question) but it does by its motion, characteristics (mass and charge) and position within the conservative electric field.
So for a similar parallel example, suppose I have an object on a table. We can say that it has potential energy relative to the floor due to the gravitational field. If I push it off, that potential energy starts to be converted to kinetic energy. We can develop a whole field of mechanics (LaGrangian) around this principle where objects are deemed to have potential energy plus kinetic energy. Do we say that the energy actually flows or is contained in the gravitational field? No, we describe the energy as being attributed to objects within the field, determined by their motion, characteristics (mass) and position within the field.
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