General > General Technical Chat
Veritasium "How Electricity Actually Works"
TimFox:
--- Quote from: Naej on June 05, 2022, 08:14:26 pm ---
--- Quote from: Terry Bites on June 05, 2022, 04:55:01 pm ---Some time back Dave pointed out that for most practical engineers it doesn’t matter. I'd agree with that. But it may or may not matter, it depends on the situation. It matters very much to ic designers and semiconductor physicists.
--- End quote ---
No it never matter.
--- Quote from: TimFox on June 05, 2022, 05:35:02 pm ---Yes, that which we call Ohm's Law is a result of the scattering of electrons by lots of things in a conductor, so that they do not achieve a high velocity from the voltage gradient along the wire.
An example calculation in https://www.macmillanlearning.com/studentresources/college/physics/tiplermodernphysics6e/classial_concept_review/chapter_10_ccr_10_mean_free_path.pdf gives a mean free path between scattering events for electrons in copper as 0.39 nm.
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This is completely incorrect.
https://homepages.rpi.edu/~galld/publications/PDF-files/Gall-116.pdf
Indicates 39.9 nm.
He assumed that electrons scatters with atoms, while they scatter with phonons.
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Yes, there are lots of things inside a conductor to scatter electrons.
In grad school, I learned about phonons, lattice imperfections, and other defects as contributions to limiting the conductivity.
Note that, in general, alloys (which include impurities) have much lower conductivity than pure metals under normal conditions.
SiliconWizard:
But electrons don't matter anyway? ;D
abquke:
"Bremsstrahlung... what? Why are you all hiding behind lead shields? I'm surely not in the path of any Poynting vectors"
TimFox:
--- Quote from: abquke on June 05, 2022, 08:32:23 pm ---"Bremsstrahlung... what? Why are you all hiding behind lead shields? I'm surely not in the path of any Poynting vectors"
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Again, in grad school we had a visiting professor from Darmstadt. He was giving a series of lectures on electron interactions. Although his English was very good, he was a little nervous about his lecture and asked an American student who was fluent in German to sit in the front row, in case he had a language problem. At one point, he asked "Wie sagt man Bremsstrahlung auf Englisch?, to which the student replied "Bremsstrahlung".
Naej:
--- Quote from: SiliconWizard on June 05, 2022, 08:25:36 pm ---But electrons don't matter anyway? ;D
--- End quote ---
Poynting vector does not matter. Electrons, obviously, do.
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