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| Electroboom: How Right IS Veritasium?! Don't Electrons Push Each Other?? |
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| Nominal Animal:
--- Quote from: SiliconWizard on June 18, 2022, 06:28:45 pm ---To sum it up, as we can't know what exactly electrons are, if we are being minimally honest, we can't answer this kind of questions properly. But we can always keep trying. :popcorn: --- End quote --- I wouldn't say that, because physics is about modeling the reality, not explaining why reality is the way it is. QM models both electrons and photons quite well; definitely well enough for simulations to produce results that are directly applicable and testable in the real world. The main thing that makes electrons different to photons is that electrons are fermions, whereas photons are bosons. Any number of photons can occupy the same quantum state, but only one electron can occupy a specific quantum state at any point in time; this is what Pauli exclusion principle is about. The exclusion principle is also why non-interacting fermions can often be treated as "Fermi gas" –– the behaviour is close to that of an ideal gas –– via Fermi-Dirac statistics. It is also why it makes sense to model the charge carriers in conductors (especially metal lattices) and semiconductors as waves (as approximations of quantum wave functions). Such models predict what happens in the real world rather well: so much so, that this is how new dopants in semiconductors (both surface and bulk) are explored, and things like memristors are explored; with the main practical problem in making the findings reality being production: how to duplicate the desired molecular structures in a commercially viable manner. The main thing I'd want people to remember, is that electrons are not spherical or even point-like particles: just like photons, electrons exhibit wave–particle duality. For example, an electron does not really orbit around an atomic nucleus: it is delocalized (in the QM sense, not in the chemical sense) in a specific waveform around the atomic nucleus, and has properties analogous to "real-world" spin/angular momentum. Because electrons are spin-1/2 particles, they have exactly two pure spin states, which are called "spin up" and "spin down". This is also why you can have exactly two electrons in otherwise the same quantum state, as long as they have different spins. This can be shown in practice: Stern–Gerlach experiment. (The field of spin transport electronics is called spintronics, in case this two-state property raised your interest for implementing binary or Boolean logic.) If you are a proponent of alternative physics models, do consider looking at e.g. the photoelectric effect, and carefully go through your alternative model and examine what kind of results it yields. If its results do not match experiments, it isn't useful, is it? You see, the photoelectric effect (and the ultraviolet catastrophe) was one of the key things that lead to the adoption of quantum mechanics as the currently best model at small scales. They didn't just "pick" one; it is the one that predicts reality and practical measurements and experiments best, thus far. |
| Naej:
--- Quote from: Nominal Animal on June 18, 2022, 04:20:50 pm ---The entire question assumes that electrons are discrete particles, but as leptons, they are not; they're firmly in the quantum realm. As an example, many interesting and useful phenomena in semiconductors and LEDs depend on surface plasmons, something that arises from the collective QM behaviour of several/many electrons. (As a practical example, the double-slit experiment shows exactly the same results for electrons as it does for photons.) One of the most annoying problems in molecular dynamic simulations is in visualization, where the goal is to convey an intuitive picture of the system or what is actually happening. The atoms are not round marbles with well defined boundaries, and electron bonds are definitely not cylindrical sticks between round marbles... It is surprising how subtly visualization choices can affect ones understanding. Which is why I much prefer eg. cel/toon shading over photorealism, and semi-transparent isosurfaces denoting a specific electron density. I want to control the information conveyed, so I can push the intuitive understanding towards something useful; photorealistic marble-and-stick models do not. Simply put, we're definitely talking about quantum interactions (of both leptons (electrons) and bosons (photons), and lepton-lepton, lepton-boson, and possibly even the rare boson-boson interactions), when we are talking about current flow. Any human-scale analogs (like "electrons 'pushing' against each other") will not describe the situation quite correctly, and will lead to misunderstandings and un-physical model ideas. --- End quote --- Mehdi's goal is not to explain renormalization, or how electrons acquire mass by interaction with the Higgs boson. Same for Derek, as far as these videos are concerned. A classical model, where electrons push against each other (and against protons), is good enough. And yet, they (and more importantly, the authors of the physics book) missed the fact that the bulk of wires is charged, due to the (tiny) Hall effect. Derek's "The main thing I like to think about the battery doing is maintaining this distribution of surface charges" is a strange and confusing statement, if anything, "the only role of the surface charges is maintaining the electric potential" is a better one. Also Derek said there's a "qualitative" distinction between electrons bringing electrons, and vacuum, which may be true, but there is no physical distinction. |
| Nominal Animal:
--- Quote from: Naej on June 19, 2022, 12:18:18 am ---Mehdi's goal is not to explain renormalization, or how electrons acquire mass by interaction with the Higgs boson. Same for Derek, as far as these videos are concerned. A classical model, where electrons push against each other (and against protons), is good enough. --- End quote --- It is good enough to model the effects, yes; but the description then must be understood as an analog, not a precise description of what is happening, because we can easily construct other experiments and situations where it does not suffice at all. You cannot use the approximation as a basis for your description! As an example, consider the Lennard-Jones potential, which describes electrically neutral atoms, like noble gases (especially neon), using a pairwise interaction model. If you do not realize that it is just an approximation where the repulsive term (1/r12) is intended to describe Pauli exclusion repulsion at short ranges and the attractive term (1/r6) describe the (London) attraction at longer ranges, and for these kinds of systems these two describe the interactions well enough, you might start discussing numerological meanings of the exponents -12 and -6. Especially because the pairwise Coulomb potential of point-like charges is ~ 1/r. The true reason for the exponent -6 is so called London dispersion force, which is described by quantum mechanics (and is basically "electrons symmetrically distributed around separate atomic nuclei will spontaneously be attracted towards each other"). The reason for the exponent -12 is simply that it is in the right ballpark – anything that increases fast enough when r decreases works for Pauli exclusion at short ranges; it just must not contribute (much) at longer ranges –, and that 1/r12 is easy to calculate from squaring 1/r6, i.e. as (1/r6)2. Heck, you can even use 1/r for the repulsion, if its contribution at longer ranges gets canceled out somehow. |
| electrodacus:
I was hopping Mehdi had a better understanding so that it can convince Derek that he is wrong. I still think that understanding the capacitor is the thing people should concentrate on. Replacing the battery with a charged capacitor will better help visualize what stored energy is and how energy travels from source (charged capacitor) to Load (lamp/resistor). What is the difference between a charged capacitor and a discharged one ? The only difference is the ratio of electrons with the discharged capacitor having the same amount of electrons on both plates and the charged capacitor having and imbalance of electrons between the plates. So while a discharge capacitor has the same amount of electrons as a charged one the fact that there are more on one plate and less on the other means it contains stored energy. If you allow the electrons from the plate with excess to move to the plate with deficit you create an electric current (defined as a stream of charged particles in this case electrons). This electrons can only move from one plate to the other through a conductor (assuming capacitor is used within spec not higher voltage and ignoring the small amount of leakage through dielectric). You do not need to understand quantum mechanics to understand that energy travels through wire and not outside the wire as Derek claims. Of course energy can flow outside the wire in the form of photons (like the infrared photons do to wire heating) and even electrons can flow outside the wire giving higher enough potential (voltage) and or with combination of heat like on those old vacuum diodes someone mentioned in the other thread. And in that particular case where electrons travel through air or vacuum energy is transferred outside the wires as there is a real current through air/vacuum due to charged particles (electrons) traveling through that space. In Derek's low voltage experiment there were no electrons traveling outside the wire meaning all energy arriving at the lamp traveled through wire. |
| eti:
This pointless debate has been ongoing FAR too long. Even if there WAS a definitive "right" answer, who cares! :palm: |
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