electron flow
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David Castor
Senior Member
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- Washington, USA
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This is called the "drift velocity". It is a function of current and the number of free electrons. Copper and aluminum have huge numbers of free electrons so the drift velocity is low - on the order of 1 mm/sec. The higher the current the higher the drift velocity. Higher voltage increases the current.
ggunn
PE (Electrical), NABCEP certified
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Yes, but the actual speed of electron flow in DC current in a conductor is actually very slow compared to the speed of the current itself. As someone else pointed out, in AC current the net electron flow over time is zero since first they move one direction and then they move the other.
LarryFine
Master Electrician Electric Contractor Richmond VA
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No, the greater voltage causes greater current (all other things being equal), which causes a greater current density, not speed. Electrons moving is current, not voltage.
As for current flow, think of a hose filled with marbles. Push a new marble in one end, a marble pops out of the other end. Not the same marble, but the effect is instant.
If you increase the Voltage at the same current, you could think of the Voltage as the Potential Energy, PE is increased directly proportional.
The current, Amps, is charge per unit time. Amps in your problem statement, the current does not change. So both current density and drift velocity do not change.
If the current flow, Amps in your problem statement, do change, then electrons, charge per unit time passing the sample point, change directly proportionally. Actually whether is increased charge density or increased drift velocity idk. It's a good question.
My guess would be is, charge carriers, the conduction electron, are limited by the number of conductor atoms (copper or AL) in the cross section at the sample point. That number of atoms is fixed by the circuit geometry. Assuming the current increase does not cause additional electrons to pop up into the conduction band (maybe idk), Then charge density would be fixed and the current increase would be an increase in drift velocity.
The total of each conductor atom at the sample point cross section would be a fixed number. The number of conduction band electrons they donate to the flow could be a fixed number or it may increase under certain conditions. My guess would be that conduction band electrons per conductor atom would be a fixed number within the range of your problem statement (someone here might fill in the blank)
So current flow would be charge per unit time. Charge would be the charge density x the cross section. And the question would be does the voltage increase cause more electrons per atom to jump to the conduction band.
For the sake of understanding what flows in the wire, I believe at the quantum level they admit that they do not know. The bulk matter properties, much is known.
It's interesting to read the original in their own words. If you ask about the underlying physical reality at the level of the individual electron, they chose a model that ignores the "physical reality". That makes it dangerous to relate it to mechanical analogues.
jaggedben
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Current isn't actually electrons moving. It's more like the transmission of charge.
A better analogy is a Newton Pendulum, which allows people to visualize how matter can transmit energy without really moving at all.
jaggedben
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Yeah, something like 299,792,458,000 times slower, using David's number. I think you might want add some verys.
LarryFine
Master Electrician Electric Contractor Richmond VA
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Just trying to keep it simple for the newbies.
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Except in the impossible ideal case, there is indeed motion. Just over a very short distance compared to the size of the ball. (Relativity tells us that nothing can be infinitely rigid.)
jaggedben
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Right. They don't move ... much.
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More to the point, all of the conduction electrons from one end or a uniform copper wire to the other move the same distance per unit time, unllike the balls in the Newtons Cradle.
(And I am referring to the instantaneous velocity, not just the average velocity of zero for AC.)
I am not sure there is any mechanical analogue that could be applied. That's in the earlier link, the Heisenberg pdf, specifically says it's not billiard balls.
I know at that time in the 1930's they started with the "planetary model" of a point charge in orbit around the nucleus, but then there was the problem with the model of the non radiation condition of the stable bound state. A point charge in motion would radiate. If H with one bound electron radiated it would be unstable, which is not observed.
Mills says the electron has the shape of a two dimensional great circle, as a trial mathematical solution. I don't know what he says about conduction in a wire but I know where to look. He wrote his own GUT.
I don't see how the mass of the electron moving could "cause" conduction. The inertia mass effect would be too slow, probably by many orders of magnitude compared to light speed, and probably take some excess energy to get the mass moving. It's possible conduction is mostly a massless effect. The electron would be affected by conduction and participate rather than cause it. An electron in a higher energy conduction state would have a larger (stable known) radius. QM says the radius could be any number.
I do think they could actually teach what the electron really is. What is it about the underlying structure of the universe that causes the electron to exist. But they don't do that at all, so it's something they could do a better job about. The underlying structure is obfuscated by the present non physical descriptions (Heisenberg).
There's a problem what just that and trying provably false already discarded models to describe "what is" is part of the problem.
Mills has the best handle on it imo. And he's making hundreds of kW of steam with it.
I know at that time in the 1930's they started with the "planetary model" of a point charge in orbit around the nucleus, but then there was the problem with the model of the non radiation condition of the stable bound state. A point charge in motion would radiate. If H with one bound electron radiated it would be unstable, which is not observed.
Mills says the electron has the shape of a two dimensional great circle, as a trial mathematical solution. I don't know what he says about conduction in a wire but I know where to look. He wrote his own GUT.
I don't see how the mass of the electron moving could "cause" conduction. The inertia mass effect would be too slow, probably by many orders of magnitude compared to light speed, and probably take some excess energy to get the mass moving. It's possible conduction is mostly a massless effect. The electron would be affected by conduction and participate rather than cause it. An electron in a higher energy conduction state would have a larger (stable known) radius. QM says the radius could be any number.
I do think they could actually teach what the electron really is. What is it about the underlying structure of the universe that causes the electron to exist. But they don't do that at all, so it's something they could do a better job about. The underlying structure is obfuscated by the present non physical descriptions (Heisenberg).
There's a problem what just that and trying provably false already discarded models to describe "what is" is part of the problem.
Mills has the best handle on it imo. And he's making hundreds of kW of steam with it.
jaggedben
Senior Member
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Let me be clear: the Newton Cradle analogy does not intende for the balls to represent electrons, atoms, charges, or any other particular thing involved in electricity. It is merely to point out another instance in which matter can transmit energy from one end of a thing to another, on a macroscale, without the transmitting matter having to journey the same distance the energy does. In one case it's kinetic energy, in another case it's electric, so the similarities end there.More to the point, all of the conduction electrons from one end or a uniform copper wire to the other move the same distance per unit time, unllike the balls in the Newtons Cradle.
(And I am referring to the instantaneous velocity, not just the average velocity of zero for AC.)
That said, the analogy is best when you consider what happens in the Newton's Cradle when only one ball swung at the end, resulting in only ball being swung at the other. The balls in the middle do in fact, move the same distance per unit time, to the extent they move much (although the point is they that don't move much, compared to the ones on the end).
(Also, to be clear, the analogy only holds for one swing of the cradle.)
Just like this.
nypost.com
You could read this but you have to know what to look for.
The picture of the floating disk is obviously not of the story subject matter. In the fine print you can see it says "Getty stock photo". But for the average reader I would guess they think the news story and the photo go together like "look we have done this". No, the photo is from a superconductor that needs cryogenic freezing. Unrelated to the story.
Second, look but you will not be able to find any real world understandable explanation of the mechanism of operation. They have achieved an n-manifold calculation that clears the Fermi level. Bracketed by click bait hype "this will take humans to the next level".
I don't doubt it is a great achievement. But I don't see anywhere that they are able to describe what the electron actually is or what they have done to it to cause it to super conduct. They are grasping at air for an explanation of what is it they have done.
LK-99 superconductor research breakthrough could mark ‘new era for humankind’
Firms conducting research into superconductors have seen their share prices jump since a July 22 paper from South Korean researchers.
nypost.com
You could read this but you have to know what to look for.
The picture of the floating disk is obviously not of the story subject matter. In the fine print you can see it says "Getty stock photo". But for the average reader I would guess they think the news story and the photo go together like "look we have done this". No, the photo is from a superconductor that needs cryogenic freezing. Unrelated to the story.
Second, look but you will not be able to find any real world understandable explanation of the mechanism of operation. They have achieved an n-manifold calculation that clears the Fermi level. Bracketed by click bait hype "this will take humans to the next level".
I don't doubt it is a great achievement. But I don't see anywhere that they are able to describe what the electron actually is or what they have done to it to cause it to super conduct. They are grasping at air for an explanation of what is it they have done.
In theory course, I've heard in an hour's time, DC will move an electron only a few feet. And in AC, the electron is basically just traveling back and fourth and only moving less than the diameter of a human hair.
But it's an interesting question, I think about lightning or static electricity. When there is an arc, is the individual electron jumping that distance?
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