Finding potential at the center of metal sphere

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Homework Help Overview

The problem involves finding the electric potential at the center of an uncharged conducting spherical layer with inner and outer radii R_1 and R_2, respectively, given a point charge q located at a distance r from the center. The original poster considers the method of images but questions its practicality due to the complexity introduced by the spherical conducting layer.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss various methods, including the method of images and Legendre polynomials, to analyze the potential. Some express concerns about the implications of letting R_1 approach zero, while others explore the contributions to potential from induced charges on the inner and outer surfaces of the sphere.

Discussion Status

There is an ongoing exploration of different approaches to the problem, with participants questioning assumptions and clarifying concepts. Some participants have proposed potential expressions based on their reasoning, while others have raised concerns about the validity of these expressions under certain conditions. No consensus has been reached, and the discussion remains active.

Contextual Notes

The original poster later clarifies that the problem should state r < R_1, which may affect the interpretations and approaches discussed. There are also references to external sources and differing opinions on the uniform distribution of charge on the outer surface of the sphere.

  • #61
ehild, in post # 58, I am talking about the inner spherical cavity which is not necessarily concentric with the outer spherical shell. You were replying to different question in post # 55. I just generalised that in post # 58.
 
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  • #62
I see. How do you get the potential at the outer surface then?

ehild
 
  • #63
Ok

Irrespective of the shape of the cavity inside the metallic sphere, if we place the charge ,q,
inside the cavity, then equal charge q is distributed uniformly on the outer spherical surface.
The cavity and the outside are different worlds altogether as long as we are talking about
electrostatic case. So potential on the outer surface would just be \frac{1}{4\pi\epsilon_o}\frac{q}{R_2}
 
  • #64
IssacNewton said:
Ok

Irrespective of the shape of the cavity inside the metallic sphere, if we place the charge ,q,
inside the cavity, then equal charge q is distributed uniformly on the outer spherical surface.
The cavity and the outside are different worlds altogether as long as we are talking about
electrostatic case. So potential on the outer surface would just be \frac{1}{4\pi\epsilon_o}\frac{q}{R_2}

I agree with this of course, Issac. It's early in the morning for me but that sounds right.

As for your earlier query: as long as you can wrap a spherical Gaussian surface around the cavity and fully contained in metal, your statement must be true, otherwise the E field could not be zero everywhere about the surface. So it makes no difference what the shape of the metal is - it can be quite irregularly shaped - the charges in the cavity have to be distrtibuted so as to null the net field at every point on the Gaussian shell just beyond R1, just as in the concentric case. So the image would not change from the concentric c ase.
 

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