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"Veritasium" (YT) - "The Big Misconception About Electricity" ?
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TimFox:
At the quantum level, energy and time have an uncertainty relationship like momentum and position.
"Virtual" particles are created and die in very short times, temporarily violating the conservation of energy.
EEVblog:

--- Quote from: SiliconWizard on January 18, 2022, 06:45:12 pm ---The point, is, again, to see if the original example in Veritasium's video is really relevant in showing what was claimed when the system reaches steady state.

--- End quote ---

The question was clearly intended toward getting the 1/c instant response.
The question could also of course be used to show transient behaviour without any reference to Poynting or Maxwell at all. It could be used as just interesting tricky circuit fundamentals question.
adx:

--- Quote from: SiliconWizard on January 18, 2022, 06:45:12 pm ---Note that I was merely talking about, say, two pieces of wire - ideally with zero resistance. Just like in the original circuit. With no significant heating.
The point was not to reinvent the vacuum tube. Now the alternative to heating that I know of (cold cathode) requires ionizing some gas, so it wouldn't work in a vacuum. But please elaborate, because I'm pretty sure I've missed something. Just keep in mind it shouldn't require more than "wires" in a vacuum.

The point, is, again, to see if the original example in Veritasium's video is really relevant in showing what was claimed when the system reaches steady state.

--- End quote ---

Yes, that's exactly what I mean - wires, DC, vacuum, and Poynting. But it's hardly anything controversial or new it turns out. I even spelled it out a fair few pages back but no one seemed to notice so I left it hidden in plain sight in the hope I might work it out. More a technicality of the wording, than any useful power transfer unfortunately! What I was more interested in was deriving something Poynting-like to illustrate why that weirdness works. But I think my "Got it" post is far more useful, the key to that is the energy moves along at the speed of light. Some weeks back now I worked out (didn't post) the longitudinal wave (acoustic) velocity of the electron fluid in a wire if acting on its neighbours only, based on the assumption of compressibility same as bulk metal (where the effect is basically that) and rest mass of electrons rather than whole metal ions. That is much slower than the speed of light, which shows that there has to be some longer-range field / interaction effects. The Poynting vector is of a phenomenon that travels at the speed of light, so can't be expected to have a direct physical relevance to something that moves slower. The energy has to transfer from each 'cell' (whatever that is) to the next at the speed of light, whatever the frequency, if there is to be a "flow" of something tangible (rather than a "flux" of something intangible which we are desperately trying to avoid treating energy (and therefore matter) as). I'd guess, like most things wavey, that it is the sum of a whole lot of small contributions, like the way a line of circular point sources sums to produce a line wave, that produces the result. And electrons moving to offset fields that would otherwise show energy flow (because they are carrying it in a different form / view) makes it appear zero in the wire, not any fact that it is zero. This isn't about searching for an accurate model (which we have), but understanding of something that appears incorrect.

Oops, walltext. The second paragraph will have to wait. And some other replies.
adx:

--- Quote from: Naej on January 16, 2022, 07:57:06 pm ---adx: if you follow Poynting then copper wires are the low-frequency equivalent of light fiber, a transformer is impedance matching, and a resistor is a low-frequency black-body.

--- End quote ---

I'm reasonably happy with that occult-like thinking. Metal is a shiny reflector, transformers are used in RF for purposes other than isolation, and a microwave-powered incandescent emitter might not be such a silly thing in some piece of equipment. But there comes a point where even the silliest engineer will reject something too silly for even their silliest of comedic senses :).


--- Quote from: Naej on January 16, 2022, 07:57:06 pm ---For acoustic waves, half the energy is in the pressure, and half in the velocity (much like in light, half is in E, half is in B).

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I'm fairly sure if I learned facts such as that (for E and B) and it was presented as something understandable, then EM would have made a lot more sense to me. Instead I got invisible mathematical concepts, and things like the graph you see so often repeated (with the arrows, that I can only assume is as utterly opaque to others starting from nothing as it was to me - no one says it is a graph of field strengths along the line of propagation, leaving less mathematically inclined people to guess it is a picture of some kind of magical aether strings being poked at by sharp sticks which physically wave about).

Anyway, the acoustic wave thing might help explain (to others and myself) about Poynting and the 'difference' between DC and steady state.

A hydraulic circuit works a bit like an electric circuit (balls in a pipe), so turning on a switch (opening a valve) allows pressure to 'flow' at the speed of sound to the load, and current flows at the same time. This description (and hence model) of course has little to do with the pieces of fluid that carry the pressure and end up in the load, it's about a pressure wave causing the molecules to accelerate and flow almost instantaneously (compared to how long it would take the fluid to go around the circuit). Once this transient settles, and flow becomes steady state, nothing changes in the nature of how energy is delivered to the load - it is still described by a transverse (between pipes) pressure difference being sent back and forth, and how fast all the fluid molecules are moving around the circuit. If either end changes the pressure, the other end will see it at the speed of sound. Same if poking at something with a stick. If modelling that, a wave effect governs that transfer of pressure at only two possible velocities: + and - speed of sound (to and from load). Anything which uses that model to calculate power, can only assume it travels at that same speed and from a transverse pressure difference. If DC steady state, there are still molecules pushing on each other electrically, with mass, and a limit to how quickly that can do work at the other end.

For a hydraulic circuit at DC it is easy(er) to poo-poo the notion of a Poynting-like vector where the current is represented by some out of pipe "field", because the momentum part of the wave transfer is due to the inertial mass of the molecules (which is thought to reside in the molecules and pipe). It also doesn't change, so the energy transferred via pressure isn't mediated by the mass (so you could then turn around and say it clicks over to infinite speed at exactly 0Hz).

But for an electrical circuit, the momentum arises from electrical field effects, which can be outside the wire. Because the momentum isn't located to inside the electron, it is possible that the field changes as it passes by other parts of the circuit - with no net energy change but more possibility for action than with a particle with internal inertia.

And oops that's me again for the night.
bsfeechannel:

--- Quote from: EEVblog on January 16, 2022, 05:38:51 am ---Derek has done an an entire video on how he is deliberately chasing the algorithm and views. he's quite up front about it and explains his reasons at 14:45 and I think they are solid. And I know he's genuine about wanting to get mainstream people into science.



--- End quote ---

I think the "clickbating" aspect of his videos are of secondary importance. In this other video he discusses how misconceptions restrain people's ability to learn. That's why all Vertitasium videos start discussing the misconception first and then they introduce the scientific concept about the topic, because he saw that, that way, people invest mental effort in watching his videos and actually learn.

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