Speed of electron flow through a conductor

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Discussion Overview

The discussion revolves around the speed of electron flow through conductors, specifically copper, and whether it is equivalent to the speed of light in a vacuum ('c'). Participants explore concepts related to electron drift velocity, the propagation of electromagnetic fields, and the relationship between electron speed and energy transfer in electrical circuits.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions whether the speed of electron flow in conductors is equivalent to 'c', noting that it cannot be exactly the same due to the medium being a conductor rather than a vacuum.
  • Another participant explains that the speed of electrons in a conductor is measured in cm/s, while the electromagnetic field propagates at a speed approaching 'c', drawing an analogy to water flow in a pipe.
  • A third participant introduces the term "electron drift" and provides a link for further reading on drift velocity.
  • Further clarification is provided that while the electromagnetic field travels at a speed close to 'c', the actual drift speed of electrons is much slower and varies based on different parameters.
  • One participant challenges the notion that the energy carried by the current is related to the kinetic energy of the flowing charges, emphasizing the low mass and speed of individual electrons compared to the energy transferred in a circuit.

Areas of Agreement / Disagreement

Participants generally agree that the speed of electrons is not equivalent to 'c', but multiple competing views remain regarding the implications of electron drift, the propagation of electromagnetic fields, and the nature of energy transfer in circuits.

Contextual Notes

There are limitations in the discussion regarding the assumptions about electron drift velocity, the definitions of speed in different contexts, and the relationship between kinetic energy and energy transfer that remain unresolved.

rootone
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Is the speed of electron flow through a conductor such as copper equivalent to 'c'?
I've heard of this being implied several times, but is it a fact?
I know it can't be exactly the same as 'c' because we are not talking of energy propagating though a vacuum.
 
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I'm not an expert but I know the speed of electrons in a conductor like copper is measured in cm/s.
It's the electromagnetic field that propagates with such a speed: in fact when we turn on the light the sensation is that there isn't delay in trasmission of current.
This fact is similar to open a tap or faucet on a pipe; a pressure wave propagates through and water, which has a smaller speed, goes out because the pipe is already full of water.
 
Thanks both.
So 'c' is not actually a relevant factor at all, although the electromagnetic field generated by a current does travel at a speed approaching c.
(whereas the actual drift speed of electrons themselves is nowhere near c and can vary depending on various parameters).
 
Furthermore, there is another mistaken idea that the energy carried is something to do with the Kinetic Energy of the flowing charges. A moment's thought should put that to bed when you consider the mass of a single electron (1/ (many thousands) of each atom) and a mean speed of a few mm/s and then think of the energy transferred by the charges in a circuit.
 

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