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| "Veritasium" (YT) - "The Big Misconception About Electricity" ? |
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| SiliconWizard:
--- Quote from: SiliconWizard on December 31, 2021, 07:34:58 pm --- --- Quote from: SandyCox on December 31, 2021, 04:00:52 pm --- --- Quote from: SiliconWizard on December 30, 2021, 06:33:58 pm ---So now, let's study the same setup, but with a circular wire loop instead of a rectangular one. :) --- End quote --- I assume we are talking about two circular loops, replacing the two rectangular loops? --- End quote --- Uh. Sometimes, words are poor at expressing simple things. So, what I meant was essentially something like this: https://www.eevblog.com/forum/chat/veritasium-(yt)-the-big-misconception-about-electricity/msg3823973/#msg3823973 With the battery and switch (let's neglect the distance between those two again) diagonally opposite to the load, and R the radius of the circle. --- End quote --- So, anyone? ;) |
| SilverSolder:
--- Quote from: SiliconWizard on January 03, 2022, 07:12:42 pm --- --- Quote from: SiliconWizard on December 31, 2021, 07:34:58 pm --- --- Quote from: SandyCox on December 31, 2021, 04:00:52 pm --- --- Quote from: SiliconWizard on December 30, 2021, 06:33:58 pm ---So now, let's study the same setup, but with a circular wire loop instead of a rectangular one. :) --- End quote --- I assume we are talking about two circular loops, replacing the two rectangular loops? --- End quote --- Uh. Sometimes, words are poor at expressing simple things. So, what I meant was essentially something like this: https://www.eevblog.com/forum/chat/veritasium-(yt)-the-big-misconception-about-electricity/msg3823973/#msg3823973 With the battery and switch (let's neglect the distance between those two again) diagonally opposite to the load, and R the radius of the circle. --- End quote --- So, anyone? ;) --- End quote --- :D The whole problem is easier to digest if you start with the switch closed and then think about what happens when you open it! - then, closing the switch is just changing to the opposite sign on all your thinking, and you're done in no time at all! |
| rfeecs:
--- Quote from: bdunham7 on January 03, 2022, 06:43:55 pm ---So back to the Poynting vector. What does it mean to say that an arrow on a diagram represent power flow density in W/m2? Specifically, in the classic battery/wires/load rectangle there is a Poynting vector poynting directly away from the load on the outer side of the battery. Many diagrams conveniently omit it, Derek's video shows it but just truncates it without explaining its meaning. What does that arrow represent? Is it something tangible that can be measured, used, interfered with, etc? If I say that it is just a mathematical result (from two actual physical manifestations, E and B) that has no corresponding manifestation of its own in reality, just like the imaginary currents in the open transmission line above, can you counter that? --- End quote --- If you draw a diagram of one or two charges and draw the electric field lines, you will usually have lines that go off to infinity. We know the field drops off as we go away from the charge, so we can say the field goes to zero at infinity and most people have no problem with that. We can argue if something is physically real vs just a mathematical convenience. Examples are potential (vs just E and B field), the wave function, the Poynting vector. Then there are imaginary numbers. I'm just going to accept that these are mathematical models that engineers can use to get hopefully the right numbers. I leave it to philosophers to try to define their version of reality. |
| bdunham7:
--- Quote from: rfeecs on January 03, 2022, 07:55:33 pm ---I'm just going to accept that these are mathematical models that engineers can use to get hopefully the right numbers. I leave it to philosophers to try to define their version of reality. --- End quote --- And again, we agree. I wrote all that in a reply to your post, but I meant to direct it more generally elsewhere... |
| adx:
--- Quote from: bsfeechannel on January 03, 2022, 04:09:59 am --- --- Quote from: adx on January 03, 2022, 02:47:01 am ---I think you're probably right. But that's not certain, and no amount of introspection on the mathematical details of some theory is going to answer that last part. I get it now, and I can see the attraction. Some people just want to believe. --- End quote --- What is funny is that the Poynting theorem was independently studied by Oliver Heaviside, the same guy who developed the transmission line model, that you attempted, without success, to use to try to "debunk" Derek. His study of energy flow through fields is what made it possible for him to come up with the modern version of Maxwell's equations, without which we wouldn't have the transmission line model, nor the high frequency electronics we have today, from computers to radio. --- End quote --- An 'old' Apple M1 die is about 11mm on the side. It goes say 5GHz ooh looking it up (not an Apple fanboi but it's a nice chip) 3.2GHz, wavelength "Have aliens found you?" no click through that ad, hmm Find out by watching our video on exoplanets, no, clickbait, be strong, https://www.omnicalculator.com/physics/wavelength = 93.6851 mm. Not far off the fabled 1/10th wavelength where thumbrulers say you can ignore wave effects and treat it all as Ls and and Cs. But even if that weren't notionally so, somewhere on that schematic, perhaps sheet 47926, will be a note next to say Q15469947265 saying "layout designer - keep close to Q1 per ECO56789". It's not all about transmission lines and RF. But ~all trolling aside, for anyone reading this thread in the future or even coming in fresh right now, very few of us have tried to "debunk" Derek's video, all basically agreed with the result and its unavoidable conclusion that transient energy must travel through space. Some question his statement on the physical reality that all power flows outside of the wires at DC (or 50/60Hz in the main rendering with the LED filament bulb). Some are unsure what electricity "is", despite many years of education (and some are too sure). And some want to know what the waveforms look like. |
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