Electric potential, hollow metalic cylinder

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Discussion Overview

The discussion revolves around the electric potential variation in a hollow metallic cylinder subjected to an external uniform electric field. Participants explore the implications of boundary conditions and the behavior of electric fields within and around the cylinder, considering both theoretical and practical aspects.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant states that the potential inside the hollow cavity of the cylinder would be constant at V_0.
  • Another participant challenges this assertion, arguing that the cylinder is not closed and questions how the potential could remain constant given the external electric field.
  • This participant introduces boundary conditions, suggesting that the potential varies between V_1 and V_2, with a specified relationship to the external electric field E.
  • A further contribution notes that the behavior of the electric field is influenced by the permittivity of the cylinder and references Faraday's principle regarding shielding effects, suggesting that the electric field can penetrate the hollow space.

Areas of Agreement / Disagreement

Participants express disagreement regarding the constancy of the potential within the cylinder, with differing views on the implications of the cylinder's open structure and the effects of the external electric field. The discussion remains unresolved as participants present competing perspectives.

Contextual Notes

The discussion highlights the dependence on boundary conditions and the assumptions regarding the cylinder's structure and material properties, which may affect the conclusions drawn about the electric potential.

ale17
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A hollow metalic cylinder of radius r and length l, has potential V0 over its surface. The axis of the cylinder coincides with the z axis, and the cylinder is centered at the origin. The cylinder is placed paralel(the electric field parallel with z axis) to an otherwise uniform electric field E.
I need the variation of electric potential V with z axis.
 
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The potential inside such a cavity would be a constant V_0.
 
Why are you saying that it's constant V_0? The cylinder is not closed as far as I understand. It's like a toilet paper roll. If it were closed with lids, I'd see why, but in this case how would you explain?

The boundary conditions are V_0 on the roll, and V_1 in one side, and V_2 in the other, such that (V_2-V_1)/l = E. If V_1 = V_2 = V_0 as you say, this means that E = 0, which is the trivial case.
 
This is not perfectly valid, because it depends on the permitivity of the cylinder. According to Faraday a metall would shield away every electric field. But if you plot the field, you will see, that the field gets into the hollow space.
 

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