Electricity Without the analogies (need expert varification)

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Discussion Overview

The discussion revolves around the nature of electricity flow in conductors, particularly focusing on the propagation of electric fields and the behavior of charges within a conductor. Participants explore theoretical aspects, analogies, and specific models related to electromagnetic theory, including the concept of transmission lines (TL) and the implications of skin depth in alternating current (AC) scenarios.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about the propagation of electric fields in conductors, noting that a conductor behaves like a medium with infinite permittivity and questioning the implications for electric flux and charge movement.
  • Another participant references a previous discussion to suggest that charge accumulates on the surface of a conductor, modifying the electric field until it is parallel to the surface.
  • There is a challenge regarding whether a current-carrying wire can be considered a type of transmission line (TL), with a request for verification from knowledgeable participants.
  • One participant clarifies that while electric fields do not propagate inside a conductor in electrostatics, the situation changes when a current is present, indicating a need for further exploration of this dynamic.

Areas of Agreement / Disagreement

Participants exhibit uncertainty regarding the behavior of electric fields in conductors, with some agreeing on the distinction between electrostatic and current-carrying scenarios, while others remain skeptical about the classification of a current-carrying wire as a transmission line.

Contextual Notes

The discussion highlights limitations in understanding the transition from electrostatic conditions to dynamic current scenarios, as well as the implications of high-frequency effects such as skin depth, which remain unresolved.

tim9000
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The topic of how electricity actually flows is one of the worst answered most common questions I've seen. Best answer I've seen was here by Gokul43201:
https://www.physicsforums.com/showthread.php?t=377359&page=3

I also HATE the "shock-wave" analogy


YET I'm still confused, as I know an electric field cannot propagate inside a conductor, I have read that a conductor is like a medium with infinite permittivity. -> I've seen pictures where the conductor's free charges move to set up an apposing electric field (I think) on the surface.

Crux:
So I always thought that a conducting wire was a TM mode TL, but I haven't seen any literature supporting my assumption (from Right hand screw rule), hence I believe it to be wrong.
Am I to conclude that infact the Electric Flux does indeed flow through at least the skin-depth (if AC) of a conductor at near the speed of 'c', because the charges are able to circulate in a loop? (and thus not oppose the E-field)

It seems weird to me that the conductor would go from having what seemed to be infinite permittivity (like an isolated sphere in an E-field), to almost no permittivity, so the E-field sticks inside the conductor and don't leak out, as it often is not a straight line (wires etc).

(or an adoquate distance for high frequencies, in an antenna)


THANKS
 
Last edited:
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For anyone curious, I think I may have found half the answer to my question here:
https://www.physicsforums.com/showthread.php?t=154617&page=2
In that-
"Now, what is an EXTREME change in charge flux, is when it tries to cross the surface of the conductor: it simply can't. So all charge that wants to flow "outside" of the conductor is accumulated on its surface! And this in such a way, that the E-field is modified UNTIL it is entirely parallel to the conductor surface (because only then, no charge wants to "flow outside" and hence gets accumulated more at the surface)."Although I still wouldn't mind hearing a "no" about the wire not being a TM mode TL, from someone who knew.
 
tim9000 said:
I know an electric field cannot propagate inside a conductor,

This is true in electrostatics, but a current-carrying wire is not an electrostatic situation.
 
jtbell said:
This is true in electrostatics, but a current-carrying wire is not an electrostatic situation.

Thanks for clearing that up. Is a current carrying wire of a type of mode TL?
 

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