General > General Technical Chat
"Veritasium" (YT) - "The Big Misconception About Electricity" ?
adx:
Those replies (aetherist) are branching too fast for me to sanity check and reply to in real time. Some passes, some fails. Were I to lob the odd "XYZ sounds crazy coz A<>B" that would feel like adding either fuel to the fire or water to the flood, so I'll take a pass.
Also I'm not the best person to talk to re a conventional understanding of something like capacitance, because I just don't. To that end I'll pick a few "points I wanted to make". A couple being:
--- Quote from: aetherist on February 04, 2022, 11:11:13 pm ---
--- Quote from: adx on February 04, 2022, 02:08:14 pm --- I don't know what "free surface electrons" are, nor why they should flow at such extremely high speeds "in" the insulation (I assume you mean the interface between wire and plastic). c/1000000 is 300m/s, compared with a drift velocity of somewhere around say 0.00001m/s expected at ~~10mA in the wire. (That's about 10000000 times slower.) It doesn't sound like you mean a skin effect, where electrons go fastest in the outer portion of a wire.
--- End quote ---
Free (surface) electrons are my idea. They are conduction electrons that live on the outside of a wire. On a bare wire they might flow at say c/10,000 in air, & a bit faster than c/10,000 in vacuum -- & say c/100,000 (ie 3 km/s) in the (air in the porous) plastic insulation (ie the portion of the plastic touching the copper), which is 30,000,000,000,000 times faster than pseudo-electron-drift inside copper.
My flow of free electrons is not a skin effect, skin effect is inside the copper. I am happy with a concept of electron drift inside copper, & electron drift close to the surface (skin effect). But i don’t think that such drifts are significant, & i don’t like the conventional idea that electric current is due to average drift or somesuch (hence i said pseudo-electron-drift).
And i don’t like the conventional idea that slowly drifting electrons can bump each other & make a wave that propagates along a wire at nearly the speed of light. Especially as the speed of em radiation in copper is (i think) 10 m/s.
--- End quote ---
(And subsequent)
Ok, I see your idea is a guess (theory). It aligns with the conventional conception "surface charge" (except for your guesses at mobility and speeds). I've seen respectable references that say for example that the charges in a Van de Graaf generator dome "move quickly to the outside". Do they swiftly go through the metal to do so? Or do they scoot around the surface to the outside, as some kind of rapid redistribution? Similar confusion surrounds Leyden jars around whether the charge resides in the water, or exactly on its surface. It appears you are with the conventionalists on this one, always with incomplete or incoherent mental depictions of some physical reality - which may be correct but all your (you, and conventionalists) explanations are clear as mud to me. Ok yours makes a bit more sense, in that the electrons that do the work are already on the surface, by definition, so they don't have to take some mystical journey to get there (yet once there, they go on another one, somehow, hence - mud). Except how do you explain skin effect if the "conduction electrons" are only at the surface? (BTW the surface charge idea is that only the excess electrons necessary to support a voltage are on the conductor, not that the majority involved in current are on the surface, so I'm not using logic in my argument, but that seems to have long since left the window.) Henry Cavendish was one of the first to dream up the concept of charge moving to surfaces, but back then things had barely moved on from electrostatics, and "charge" had a subtly different meaning (one you touched on; stored energy, in the sense of gunpowder).
In more seriousness, Gauss's law has been misapplied for conductors. The story going something like this (lifted from https://www.miniphysics.com/uy1-gausss-law-for-conductors.html):
--- Quote ---Claim: When excess charge is placed on a solid conductor and is at rest (equilibrium), it resides entirely on the surface, not in the interior of the material.
Reason: The electric field within the conductor must be zero. If there is an electric field, the charges will move. As the electric field within the conductor is 0, by Gauss’s law, there must be no charges enclosed within the Gaussian surface.
--- End quote ---
Imagine an infinite region of finite charge density - that will have zero electric field all throughout, plenty of electric potential as a constant, but all Gaussian surfaces will enclose charge. Thus proving the above wrong.
It's all fine until Gauss's law is brought into play: A compressed electron gas will have an absolute potential (or pressure) in a metal. We call it voltage these days. Electron charge will redistribute until the macroscopic gradient of the scalar potential field is zero (electric field is zero), confined by the 'energy well' of the surface of the metal (electrons don't want to go very far outside of the crystal lattice of the metal) for some surface charge but not representing the entire contents of the metal's electron gas. But zero electric field at all points doesn't equate to a region say to the left of each point containing zero charge, when an equivalent region to the right will cancel a flux emanating from the left. This is very much not unlike the same problem we've had in this thread with the Poynting vector vs its surface integral. Perhaps the 'proof' has been confused with using a Gaussian surface to generate a valid virtual surface charge.
Hence this flat Earth we've all been living in (oops, force of habit, on).
Re any dislike for the idea of very slow electron drift being responsible for potentially enormous currents (I guess that's the reason for your surface electron idea), remember this is not up to the electrons struggling against resistance in the wire. They drift exactly the same speed in a superconductor, where there's zero resistance. They go slow because they carry a lot of charge, compared to how many there are, and our relatively non-cosmic use of electricity (as in I've got this spinning black hole, and I'll just put this ring resonator around it sort of shenanigans - we like to look at 200uA flowing down 1km of cable on a farm). They go at a speed determined by the current which we want to flow. I for one am pleased that it is so sedate - rather than some horridious electromigratory copper-splattering mess. Not all the time, anyway.
But fire, water, no.
Naej:
--- Quote from: adx on February 09, 2022, 05:04:17 pm ---Imagine an infinite region of finite charge density
--- End quote ---
So with infinite potential everywhere, and with an electric field undefined?
--- Quote from: adx on February 09, 2022, 05:04:17 pm --- - that will have zero electric field all throughout, plenty of electric potential as a constant, but all Gaussian surfaces will enclose charge. Thus proving the above wrong.
--- End quote ---
Nah it's correct: in statics, no current, potential is constant in a conductor.
aetherist:
--- Quote from: adx on February 09, 2022, 05:04:17 pm ---Those replies (aetherist) are branching too fast for me to sanity check and reply to in real time. Some passes, some fails. Were I to lob the odd "XYZ sounds crazy coz A<>B" that would feel like adding either fuel to the fire or water to the flood, so I'll take a pass.
Also I'm not the best person to talk to re a conventional understanding of something like capacitance, because I just don't. To that end I'll pick a few "points I wanted to make". A couple being:
--- Quote from: aetherist on February 04, 2022, 11:11:13 pm ---
--- Quote from: adx on February 04, 2022, 02:08:14 pm --- I don't know what "free surface electrons" are, nor why they should flow at such extremely high speeds "in" the insulation (I assume you mean the interface between wire and plastic). c/1000000 is 300m/s, compared with a drift velocity of somewhere around say 0.00001m/s expected at ~~10mA in the wire. (That's about 10000000 times slower.) It doesn't sound like you mean a skin effect, where electrons go fastest in the outer portion of a wire.
--- End quote ---
Free (surface) electrons are my idea. They are conduction electrons that live on the outside of a wire. On a bare wire they might flow at say c/10,000 in air, & a bit faster than c/10,000 in vacuum -- & say c/100,000 (ie 3 km/s) in the (air in the porous) plastic insulation (ie the portion of the plastic touching the copper), which is 30,000,000,000,000 times faster than pseudo-electron-drift inside copper.
My flow of free electrons is not a skin effect, skin effect is inside the copper. I am happy with a concept of electron drift inside copper, & electron drift close to the surface (skin effect). But i don’t think that such drifts are significant, & i don’t like the conventional idea that electric current is due to average drift or somesuch (hence i said pseudo-electron-drift).
And i don’t like the conventional idea that slowly drifting electrons can bump each other & make a wave that propagates along a wire at nearly the speed of light. Especially as the speed of em radiation in copper is (i think) 10 m/s.
--- End quote ---
(And subsequent)
Ok, I see your idea is a guess (theory). It aligns with the conventional conception "surface charge" (except for your guesses at mobility and speeds). I've seen respectable references that say for example that the charges in a Van de Graaf generator dome "move quickly to the outside". Do they swiftly go through the metal to do so? Or do they scoot around the surface to the outside, as some kind of rapid redistribution? Similar confusion surrounds Leyden jars around whether the charge resides in the water, or exactly on its surface. It appears you are with the conventionalists on this one, always with incomplete or incoherent mental depictions of some physical reality - which may be correct but all your (you, and conventionalists) explanations are clear as mud to me. Ok yours makes a bit more sense, in that the electrons that do the work are already on the surface, by definition, so they don't have to take some mystical journey to get there (yet once there, they go on another one, somehow, hence - mud). Except how do you explain skin effect if the "conduction electrons" are only at the surface? (BTW the surface charge idea is that only the excess electrons necessary to support a voltage are on the conductor, not that the majority involved in current are on the surface, so I'm not using logic in my argument, but that seems to have long since left the window.) Henry Cavendish was one of the first to dream up the concept of charge moving to surfaces, but back then things had barely moved on from electrostatics, and "charge" had a subtly different meaning (one you touched on; stored energy, in the sense of gunpowder).
In more seriousness, Gauss's law has been misapplied for conductors. The story going something like this (lifted from https://www.miniphysics.com/uy1-gausss-law-for-conductors.html):
--- Quote ---Claim: When excess charge is placed on a solid conductor and is at rest (equilibrium), it resides entirely on the surface, not in the interior of the material.
Reason: The electric field within the conductor must be zero. If there is an electric field, the charges will move. As the electric field within the conductor is 0, by Gauss’s law, there must be no charges enclosed within the Gaussian surface.
--- End quote ---
Imagine an infinite region of finite charge density - that will have zero electric field all throughout, plenty of electric potential as a constant, but all Gaussian surfaces will enclose charge. Thus proving the above wrong.
It's all fine until Gauss's law is brought into play: A compressed electron gas will have an absolute potential (or pressure) in a metal. We call it voltage these days. Electron charge will redistribute until the macroscopic gradient of the scalar potential field is zero (electric field is zero), confined by the 'energy well' of the surface of the metal (electrons don't want to go very far outside of the crystal lattice of the metal) for some surface charge but not representing the entire contents of the metal's electron gas. But zero electric field at all points doesn't equate to a region say to the left of each point containing zero charge, when an equivalent region to the right will cancel a flux emanating from the left. This is very much not unlike the same problem we've had in this thread with the Poynting vector vs its surface integral. Perhaps the 'proof' has been confused with using a Gaussian surface to generate a valid virtual surface charge.
Hence this flat Earth we've all been living in (oops, force of habit, on).
--- End quote ---
My new electricity invokes lots of ideas (some old some new). One idea is that there is a concentration (a sea) of free-ish electrons on the surfaces of a wire. This concentration (surface) effect arises naturally at all times on all wires because (as u get closer to a surface) there are more electrons pushing (other electrons) out towards the surface compared to in away from the surface. Hence some (conduction electrons) move to the surface. At the same time we must have a depletion of electrons inside the wire. Free-ish (surface) electrons might spend most of their time being free-ish & very little time being orbital.
Likewise there must be an additional concentration (end) effect of free-ish electrons on the surfaces near the ends of wires, because as u get closer to an end there are more surface electrons pushing out towards the end. At the same time we must have a depletion of surface electrons near mid-length.
So now we have two kinds of surface concentration effect. Here i am talking about an isolated wire, that isn’t grounded. These two concentration effects are what gives us the very concentrated charge at a sharp point.
I said the surfaces of a wire, here i mean all surfaces, outside & inside. A surface will usually involve a metal & a gas, but it might be the surface of one metal touching a different metal (not important today). I think that electrons can concentrate on an internal surface in a wire, ie giving a local negative charge.
Every elementary particle (eg electron) has a charge, & the particle emits an electric field which can be represented by straight lines radiating straight out to infinity for eternity, at the speed of light say. Negative & positive fields add or cancel. I don’t think that they annihilate. I think that a wire has fields inside as well as outside. What we usually consider is the nett fields, & imaginary lines representing nett fields. These imaginary lines are often curved. These lines do not end at a charge, they dont even start at a charge. Today we have experts who think that such lines are real. Even Dollard reckons that an electron is simply an end of a line that has gone adrift.
Re charges in a Van de Graaf dome moving through the metal or scooting around the surface. I think that here we have every kind of drift (inside) & flow (outside) & propagation of charge (inside & outside) & propagation of electrons (outside) at various speeds. If the charge is due to electons (photons hugging the surface)(electons have a negative charge) then these electons will redistribute around on the surface at the speed of light c/1. If the charge or a part of the charge is due to electrons then these will flow around on the surface at say c/10,000. And during this time all electons & electrons emit an electric field that propagates through the dome & creates surface electrons on say the opposite side, however the propagation through the dome would be at only say c/30,000,000 (because the speed of em radiation in copper is only say 10 m/s). And at the same time internal electrons will drift through the dome at say 0.0001 m/s (ie no help here).
Re skin effect, if u explain the problem then i will see if i can explain how new electricity fits. Offhand i am thinking that free-ish surface electrons suffer resistance to flow & hence they heat the surface of the wire. And at the same time internal conduction electrons resist drift & hence they heat the inside of the wire.
Re Leyden jars containing water, i think that water rules out my electons (which i don’t think propagate on or through water), but i don’t know whether that is fatal to my new electricity.
Cavandish might have been one of the first to dream up the concept of charge moving to surfaces. But i can report that he was followed by Veritasium in 2021 & by AlphaPhoenix in 2021.
At 6:15 & 7:00 in Veritasium's youtube he says….
…. the electric field pushes electrons around so that they accumulate on some of the surfaces ….
…. this charge on the surfaces of the conductors also creates an electric field outside the wires ….
At 17:20 in AlphaPhoenix's youtube he says….
…. now imagine an electron sitting on the wire just left of the bulb – it is free to move ….
My new electricity consists of (or can consist of) (1) electons propagating on a wire, & (2) electrons flowing on a wire, & (3) electrons drifting in a wire (insignificant). The proportions of (1) & (2) will depend on the kind of source (eg lead acid battery).
--- Quote from: adx on February 09, 2022, 05:04:17 pm ---Re any dislike for the idea of very slow electron drift being responsible for potentially enormous currents (I guess that's the reason for your surface electron idea), remember this is not up to the electrons struggling against resistance in the wire. They drift exactly the same speed in a superconductor, where there's zero resistance. They go slow because they carry a lot of charge, compared to how many there are, and our relatively non-cosmic use of electricity (as in I've got this spinning black hole, and I'll just put this ring resonator around it sort of shenanigans - we like to look at 200uA flowing down 1km of cable on a farm). They go at a speed determined by the current which we want to flow. I for one am pleased that it is so sedate - rather than some horridious electromigratory copper-splattering mess. Not all the time, anyway. But fire, water, no.
--- End quote ---
The reason i don’t like drift is that it can't explain how electricity propagates at the speed of light, & especially because it can't explain how electricity propagates at the speed of light in the plastic insulation. My new electricity is a work in progress, & it might run into problems re the (too) slow speed of my electrons flowing on a wire, or i should say the (too) slow speed of the wavefront of my electrons flowing on a wire, the wavefront being much much faster, but still much much slower than the desired speed of light.
My new electricity says that electricity in a superconductor is due to electons & electrons on the surface, not so much due to electron drift inside. I might have a closer look at superconductors one day.
aetherist:
--- Quote from: SandyCox on February 09, 2022, 08:46:53 am ---
--- Quote ---But i think that it would take more than some smart elements, it would need the application of my new electricity (& the dumping of the old electricity).
--- End quote ---
:-DD
Let us know how that works out.
--- End quote ---
In my reply#1052 i mentioned that AlphaPhoenix's mind melted a bit because the currents at both terminals of his source were different. I also mentioned that AlphaPhoenix did not show us the trace for the current at his negative terminal, ie the trace for the voltage through his resistor that sits near his switch.
--- Quote ---Pinned by AlphaPhoenix 1 month ago (edited) COMMENTS AND CORRECTIONS:
Thanks to Derek at Veritasium for his blessing to make a real-world version of his gedanken experiment. If you haven't seen his video yet, you might want to go watch that for context, and I also highly recommend ElectroBOOM's video on the topic and EEVBlog's video on the topic. Electroboom's video has some simulated scope traces extremely close to what I saw IRL, and a REALLY fantastic animation (8:27) of him waving an electron around in his hand, shedding magnetic fields as it moves (Even though I ignore magnetic fields in this video - I'm trying to think of a test to find out if they matter).
CORRECTIONS TO THIS VIDEO:
The most important thing I believe I ignored in this video is the actual, physical distribution of charge in the switch-side wire while the current is starting up. How much charge travels AT the advancing wavefront and how much charge gets stuck along the wire in between the fuzzball I drew and the battery will depend on the physical size of the wires and how close they are to each other, setting their capacitance.
This charge distribution also DOES NOT look the same on both sides of the switch, although I drew it that way for simplicity.
In a later experiment (next video) my mind melted a bit as I measured the resistors on both sides of the battery and found the current going through them is different.
It doesn't change any of the logic I presented in this video, but it makes some diagrams less than perfect.
It's possible that cross-inductance between the wires contributes to the effect, using almost exactly the same diagram except the wires are connected by a magnetic field rather than an electric field. I couldn't figure out how to decouple these effects day-of, so I'm still thinking on how to test. Hopefully more to come there.
I'm sure there will be loads more - please leave comments about what I screwed up.[/color]
(7d) Similarly to (8a) if Brian showed us his trace for the resistor near the switch, i reckon that the current would have a quick spike & then fall, & after that grow in a similar fashion to the green trace.
So, Brian's X pt1 did a good job, & we are all eager to see pt2. And me myself i want to see the trace for the resistor near the switch.
--- End quote ---
Would u like to have a go at guessing what his (missing) trace looked like.
And what it should have looked like (ie based on old electricity).
And AlphaPhoenix has shown us his green trace for the voltage/current at his positive terminal (ie the green trace for the resistor sitting near that terminal).
Can u use old electricity to explain that there green trace (it starts at zero V & gradually climbs to 1.8 V at 1.2 laps (time))(trace shown in reply#1054).
AlphaPhoenix didn’t seem to be worried about the shape etc of his green trace, but he was very worried that the (missing) trace on the other side of the source was very different (i suppose that the current at both terminals of his source should be equal). AlphaPhoenix seems to imply that his green trace is easily explained with old electricity, but that the other (missing) trace is not. I suspect that it is the green trace that is more difficult to explain, but we wont know until AlphaPhoenix shows us the missing trace, which hopefully he will do in pt-2 of his X.
adx:
--- Quote from: Naej on February 09, 2022, 06:48:55 pm ---
--- Quote from: adx on February 09, 2022, 05:04:17 pm ---Imagine an infinite region of finite charge density
--- End quote ---
So with infinite potential everywhere, and with an electric field undefined?
--- End quote ---
Ok, terrible, unrealisable, example. Thanks for setting me straight. I was hoping the idea of zero electric field would come through. A test charge in such a place would experience zero force, assuming nothing else moved. That would break the proof if the test charge is zero, but that is kind of how it is worded.
--- Quote from: Naej on February 09, 2022, 06:48:55 pm ---
--- Quote from: adx on February 09, 2022, 05:04:17 pm --- - that will have zero electric field all throughout, plenty of electric potential as a constant, but all Gaussian surfaces will enclose charge. Thus proving the above wrong.
--- End quote ---
Nah it's correct: in statics, no current, potential is constant in a conductor.
--- End quote ---
Yes, I'm wrong. For a constant pressure fluid, the only source of force can be at the walls.
But I bet '99%' of moderately educated people (including me) were mislead by my description (if they tried to understand it) to the point where they began doubting their conception of statics enough to fall back to their education (faith) or admit they don't know (ignorance). Aetherist is righter than me. Maybe it's just me, but "mud" is my point, somewhat unfortunately but I had enough of an inkling to know I was on shaky ground. It's simple as it gets statics. Few people can clearly point out where it is wrong, and why, from a place of understanding.
I'll do some replying later some time, but time for a break :)
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