The model of electric flux in solids

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Discussion Overview

The discussion revolves around the model of electric flux in solids, specifically focusing on a solid metal cylinder and the behavior of direct current (DC) within it. Participants explore concepts such as the skin effect, current density distribution, and the implications of varying the cylinder's diameter.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants question the existence of the skin effect in direct current, suggesting that it only occurs with varying currents at higher frequencies.
  • There is a discussion about the behavior of electric fields in perfect conductors, with some asserting that no electric field exists inside a perfect conductor, while others acknowledge a small electric field due to resistance in real conductors.
  • One participant wonders about the distribution of electrons within the cylinder, asking whether they pass through the entire cross-section or just at the surface, particularly when considering the centers of the circular faces as current entry points.
  • Another participant states that in direct current, the current density is uniform across the cross-section of the cylinder, implying that the skin effect does not apply.
  • A question is raised regarding whether conductivity and resistance are equal at the surface and throughout the cross-section in a perfect homogeneous metal structure under direct current conditions.

Areas of Agreement / Disagreement

Participants generally agree that direct current means constant, non-varying current. However, there is disagreement regarding the implications of this on the skin effect and the behavior of electric fields within the conductor.

Contextual Notes

The discussion includes assumptions about the ideal behavior of conductors and the conditions under which the skin effect is relevant. There are also references to the properties of perfect conductors versus real-world materials, which may not be fully resolved.

dkastz
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hi there!

I have a bit stupid question:

Imagine a solid metal cylinder. We put a . Explain to me please the exact model of the direct current electric flux of the particles. Is there a "skin effect" when a direct current is in action ?
 
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dkastz said:
hi there!

I have a bit stupid question:

Imagine a solid metal cylinder. We put a . Explain to me please the exact model of the direct current electric flux of the particles. Is there a "skin effect" when a direct current is in action ?

You did not finish the sentence.

Is Direct Current means constant non varying current? If so, there is no skin effect to talk about, skin effect only happen with varying current and rather high frequency( no as high as people think!).

There is no electric field inside a good conductor like metal if you assume it's a perfect conductor. Any electric field developed inside the metal WILL cause the electrons to move in opposite direction to neutralize the field. That's the reason there is no electric field in a perfect conductor.

In real life, there is a very very ( very!) small electric field if you drive a current through as it's not a perfect conductor, a little voltage developed across the metal due to the resistance.
 
grr i just saw that i missed the sentence!

Yes. you`re right - Direct Current means constant non varying current. I am wondering what happens inside the cylinder - where do electrons pass - all over the cross section or just at the surface. For the example the two points of current are the centers of the circular faces of the cylinder. What happens if i vary the diameter of the cylinder ?
 
If it is direct non varying current, the current density in the middle is the same as close to the surface. It is all over the cross section of the cylinder. Skin effect only applies to varying current.

http://en.wikipedia.org/wiki/Skin_effect
 
Last edited:
deos this mean that in direct, non varying current, the conductivity/resistance is equal on the surface and in any point in the cross section (in case of perfect homogenic metal structure) ?
 

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