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"Veritasium" (YT) - "The Big Misconception About Electricity" ?

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SiliconWizard:
And, IMHO, we still haven't defined exactly what "energy traveling in wires" means anyway.
If by that we mean the analogy of water flowing through a pipe, that is certainly bogus. Electrons do not "flow" from point A to point B like molecules themselves do.
And yeah, I agree with Dave on this point: ultimately it's quantum field theory.

So yeah. What does "in wire" means? What is in and what is out when it comes to energy? Isn't that just a question of probabilities?

Uttamattamakin:

--- Quote from: EEVblog on December 31, 2021, 11:39:44 pm ---
--- Quote from: HendriXML on December 31, 2021, 04:18:02 pm ---
I got this one in my recommended list, which has only a few hundred views, so hence I link it here. The first half with formula's I skipped, but the 2nd half shows to me a valid point about electric fields in wires vs air gap when using quantum theory.

--- End quote ---

Very interesting, thanks for posting.
Nice explanation, sounds pretty solid to me. Quantum probability theory trumping Poynting?
I've sent this to Derek.

--- End quote ---

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.    As this video from PBS space time explains much better than me with my barely functional white boards.



For the phenomena under discussion here Quantum Electro Dynamics would find that the path of highest probability is along the wire, where all the free electrons are and can interact with eachother at inter atomic distances VS the vast 1m void between them and the bulb.   This paper on Compton scattering gives a sense of the complications that we go through in exchange for this https://www.personal.soton.ac.uk/ab1u06/teaching/qft/qft1/christmas_problems/2014/xmas_problem_solution.pdf  I did a related problem Bahaba scattering, electron positron scattering in graduate school.  It was such a big problem that it was one of only two problems on a homework assignment, we had two weeks to do it.  So my informed estimate is  that the probability of conduction along the wire is 0.999999 with a 0.000001

It would make for a boring video.  What did not make for a boring video was this one. This video does the experiment that Veritasium showed but at a real scale.  What it finds is very interesting so I won't spoil it. :)



I'll be around from time to time.  My main focus of research is gravitational wave physics though.  Thanks for watching.

bdunham7:

--- Quote from: SiliconWizard on January 01, 2022, 06:19:26 pm ---Isn't that just a question of probabilities?

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It is all just a question of probabilities, but then you have to do the math.  It isn't just the electrons that are a wave function, molecules are as well.  It's just that the probability distribution for a molecule is more localized than a free electron in a conductor.  This doesn't mean that the concept of individual electrons flowing in a wire is any less valid than water molecules flowing in a pipe.  As for whether they flow through the wire or outside of it, that was the exact point made at the end of Farmer's video--both are theoretically possible, the former is astronomically more likely.

SiliconWizard:

--- Quote from: bdunham7 on January 01, 2022, 06:34:19 pm ---
--- Quote from: SiliconWizard on January 01, 2022, 06:19:26 pm ---Isn't that just a question of probabilities?

--- End quote ---

It is all just a question of probabilities, but then you have to do the math.  It isn't just the electrons that are a wave function, molecules are as well.  It's just that the probability distribution for a molecule is more localized than a free electron in a conductor.  This doesn't mean that the concept of individual electrons flowing in a wire is any less valid than water molecules flowing in a pipe.

--- End quote ---

Oh really... Well, if you think QFT, or at least a part of it, can be applied to molecules, you must be following pretty recent advances in physics research: https://www.nature.com/articles/s41567-019-0663-9
because, before that, I don't think it was all that well established. Oh, and it's still partial, and the experiment, although interesting, certainly needs to be reproduced by others and more work is definitely needed on this. OK, that's for big molecules. But even for single atoms - I do think while we have indeed been able to assign them some wave functions, it's already not quite in the same territory AFAIK. Complex matter for sure. But, if that what you were thinking about, is molecular agitation really comparable to the movement of electrons, that's a tough one?

But, 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".


--- Quote from: bdunham7 on January 01, 2022, 06:34:19 pm ---As for whether they flow through the wire or outside of it, that was the exact point made at the end of Farmer's video--both are theoretically possible, the former is astronomically more likely.

--- End quote ---

Well yes! But we still haven't defined while "through the wire" exactly meant, unless I missed it. Can we find a definition?

bsfeechannel:

--- Quote from: EEVblog on January 01, 2022, 01:04:53 pm ---Does the energy flow in the field around the wire or does it flow in the wire at DC? Poynting/classical field theory says outside, QFT appears to say inside.

--- End quote ---

Wait a minute, Dave. Are you faffing around the edges of physics to confirm your bias? What happened to the Ohm's law that we, engineers, "developed to give a more practical insight rather than what is actually happening at the physics level"?

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