Applying Poisson Equation for Electrostatic Potential in a Spherical Shell

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Discussion Overview

The discussion revolves around applying the Poisson equation to determine the electrostatic potential within a spherical shell that has a uniform surface charge density and a localized patch at a constant potential. Participants explore methods for solving the equation under the given boundary conditions, particularly in the context of spherical symmetry.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Exploratory

Main Points Raised

  • One participant notes the necessity of boundary conditions when solving the Poisson equation, emphasizing the importance of spherical coordinates due to the symmetry of the problem.
  • Another participant questions whether the size of the patch relative to the sphere's radius needs to be considered and suggests that using Legendre polynomials might be a viable approach.
  • A different participant proposes that numerical methods, such as relaxation methods, could be employed to solve the problem, referencing a specific resource for further details.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best method to apply the Poisson equation in this scenario, with multiple approaches and considerations being discussed without resolution.

Contextual Notes

There are unresolved aspects regarding the assumptions about the patch's size and the specific boundary conditions required for the Poisson equation in this context.

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In many book I read, problems for electrostatic potential always lead to solving Poisson equation. I saw a problem about a spherical shell carrying some amount of charges uniformly on the surface with density [tex]\rho[/tex], and then someone put a small patch on the sphere. The patch is then made a constant potential [tex]V_0[/tex] on it and everywhere else on the shell has zero potential. I would like to find the potential everywhere inside the spherical shell. In this case, how can I apply Poisson equation to do that?
 
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The Poisson equation always holds, and the given configuration is encoded in the boundary conditions. To solve a PDE you always have to give the boundary conditions. So in this particular problem, due to the spherical symmetry its best to operate in spherical coordinates, and then describe the given boundary conditions.
 
Thaakisfox said:
The Poisson equation always holds, and the given configuration is encoded in the boundary conditions. To solve a PDE you always have to give the boundary conditions. So in this particular problem, due to the spherical symmetry its best to operate in spherical coordinates, and then describe the given boundary conditions.

Do you mean the size of the patch compared to te radius of the sphere is to be known?
If in spherical co"ordinates north pole could be an answer. Would the use of Legendre polynomals work?
 
It could be done using numerical methods, for example by relaxation methods. I'm pretty sure the book "Numerical Recipes in C" covers this, if you want to look up the details.
 

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