General > General Technical Chat
Electroboom: How Right IS Veritasium?! Don't Electrons Push Each Other??
cbutlera:
--- Quote from: Nominal Animal on July 20, 2022, 09:09:27 pm ---No, you're leaving important bits out, oversimplifying the situation to fit your axiomatic model.
--- End quote ---
What a concise and insightful sentence. Like The Treachery of Images, the more one thinks about it the more there is in it.
Simplifying the situation to fit an axiomatic model is a technique that I use all the time. I expect that we all use it. As long as I realise that I am doing it and can justify doing so, then it is a very powerful tool. But if I mistake that model for the truth and say that I know, I stop thinking. As long as I keep thinking, I come to understand. That way I might approach some truth.
(Text in italics from the 1985 film Insignificance)
Naej:
--- Quote from: Nominal Animal on July 21, 2022, 08:10:48 am ---
--- Quote from: Naej on July 20, 2022, 11:12:46 pm ---
--- Quote from: Nominal Animal on July 20, 2022, 09:09:27 pm ---"Will move". No, something makes them move. That something is an electric field, which propagates through the circuit somewhat analogously to a shock wave when the circuit is first connected. Also, some of the original "potential energy" is in the form of an electric field around the charged plate; it is not exactly correct to just lump it all into "potential energy" and call it good enough.
--- End quote ---
Or maybe it is correct.
--- End quote ---
Not exactly correct means it is an approximation.
When you are arguing about exactly where the majority of the energy flow in a system is, making such approximations is exactly how you "accidentally" manipulate it to fit your pre-selected model.
Consider this question: Are the participants arguing where the energy flows, or what the setup being investigated exactly is?
To me, the disagreement stems from the latter, and is the reason why I'm not interested in their arguments and opinions, be they professors or internet celebrities or whatever else. I am too familiar with both "garbage data + good model = garbage results" and "good data + garbage model = gargabe results" already; I want to drop the garbage parts and have people spend their time on the "good data + good model = good results" case instead.
In this case, each participant has their own model. That's no good: OF COURSE their inner workings vary then, even if the results are exactly the same.
--- End quote ---
And what I mean by correct, is that it agrees with Maxwell's model of electromagnetism.
Nominal Animal:
--- Quote from: Naej on July 21, 2022, 09:23:05 pm ---
--- Quote from: Nominal Animal on July 21, 2022, 08:10:48 am ---
--- Quote from: Naej on July 20, 2022, 11:12:46 pm ---
--- Quote from: Nominal Animal on July 20, 2022, 09:09:27 pm ---"Will move". No, something makes them move. That something is an electric field, which propagates through the circuit somewhat analogously to a shock wave when the circuit is first connected. Also, some of the original "potential energy" is in the form of an electric field around the charged plate; it is not exactly correct to just lump it all into "potential energy" and call it good enough.
--- End quote ---
Or maybe it is correct.
--- End quote ---
Not exactly correct means it is an approximation.
When you are arguing about exactly where the majority of the energy flow in a system is, making such approximations is exactly how you "accidentally" manipulate it to fit your pre-selected model.
Consider this question: Are the participants arguing where the energy flows, or what the setup being investigated exactly is?
To me, the disagreement stems from the latter, and is the reason why I'm not interested in their arguments and opinions, be they professors or internet celebrities or whatever else. I am too familiar with both "garbage data + good model = garbage results" and "good data + garbage model = gargabe results" already; I want to drop the garbage parts and have people spend their time on the "good data + good model = good results" case instead.
In this case, each participant has their own model. That's no good: OF COURSE their inner workings vary then, even if the results are exactly the same.
--- End quote ---
And what I mean by correct, is that it agrees with Maxwell's model of electromagnetism.
--- End quote ---
Maxwell's model of electromagnetism doesn't talk about "potential energy". It describes the behaviour of electric fields (E), magnetic fields (B), charge density (ρ), and current density (J).
When moving from the vector field approach to the potential approach, the electric field (E) and magnetic field (B) are described in terms of an electric potential (φ, also called scalar potential) and magnetic vector potential (A) via E=-∇φ-∂A/∂t and B=∇×A, where ∇φ refers to the gradient of the electric potential, and ∇×A to the curl of the magnetic vector potential.
Thing is, the electric potential (φ) and magnetic vector potential (A) have gauge freedom. Unless you fix them (as in stick to) with some gauge, their value doesn't really describe anything; only their behaviour does.
Let's assume you do that by using say Coulomb gauge, which says that the divergence of the magnetic vector potential is always everywhere zero, ∇·A = 0. This is not an arbitrary choice, as it leads to specific properties, which are not a result of Maxwell's laws, but the result of this specific gauge applied to the potential approach to Maxwell's model. There are other gauges that can give other values to the electric potential and magnetic vector potential, but exactly the same electric field (E) and magnetic field (B). In other words, Maxwell's model does not help you in choosing the proper gauge.
Finally, the term electric potential energy describes the potential energy associated with the electric field related to the charges present, those related to the Coulomb forces I mentioned; and those only. It does not mean that all potential energy in a system that includes moving charges is in the electric field!
Can you see what I am trying to describe? That I am not saying that anyone is wrong per se, I am saying that they are using such approximations that allow their viewpoint to be true, but that also change the system being considered so that the arguers are not actually talking about the same system anymore!
electrodacus:
--- Quote from: Nominal Animal on July 22, 2022, 01:17:56 am ---Can you see what I am trying to describe? That I am not saying that anyone is wrong per se, I am saying that they are using such approximations that allow their viewpoint to be true, but that also change the system being considered so that the arguers are not actually talking about the same system anymore!
--- End quote ---
I think you forgot what the discussion is about.
How is the stored energy in say a charged capacitor transferred to the load. Is it through wires or outside the wires ?
Wire or resistor is one and the same thing so the transmission line itself is the load.
The constant electric field between the capacitor plates has no role it is due to difference in charge between the two plates that the electric field exists not the other way around.
The stored potential energy is just converted into kinetic energy. No different from air pressure storage where you have air molecules and sound speed limit in that medium vs electrons and speed of light.
Nominal Animal:
--- Quote from: electrodacus on July 22, 2022, 01:43:18 am ---
--- Quote from: Nominal Animal on July 22, 2022, 01:17:56 am ---Can you see what I am trying to describe? That I am not saying that anyone is wrong per se, I am saying that they are using such approximations that allow their viewpoint to be true, but that also change the system being considered so that the arguers are not actually talking about the same system anymore!
--- End quote ---
I think you forgot what the discussion is about.
--- End quote ---
No, absolutely not.
--- Quote from: electrodacus on July 22, 2022, 01:43:18 am ---How is the stored energy in say a charged capacitor transferred to the load. Is it through wires or outside the wires ?
--- End quote ---
It depends on the geometry of the wires.
--- Quote from: electrodacus on July 22, 2022, 01:43:18 am ---Wire or resistor is one and the same thing so the transmission line itself is the load.
--- End quote ---
The geometry of the transmission line determines how the energy flows!
If you use a coaxial cable, the initial pulse is a waveform with lots of high-frequency components, and they will propagate as an electromagnetic field in the dielectric insulator between the core and the shield. As described by the transmission line model, you'll get reflections (of those waves) until the system reaches steady state. Then, in the steady state, the electromagnetic field in the dielectric stays constant (except for thermal noise and external perturbations), and the energy flows within the core conductor, as current.
Something very similar happens when the circuit is disconnected, too. Because of those constant fields, the circuit doesn't just immediately cease, as the remnant EM fields do their reflection stuff again.
If you ignore those initial non-equilibrium states, you do not have a full physical picture or model of what is happening. By using approximations that ignore those, and by not defining the properties of the transmission lines in sufficient detail, you can make and prove any claim correct. It is a useless argument.
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