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dcnairb
- 11
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Homework Statement
I have a hollow, grounded, conducting sphere of radius R, inside of which is a point charge q lying distance a from the center, such that a<R. The problem claims, "There are no other charges besides q and what is needed on the sphere to satisfy the boundary condition".
I have to calculate V and I'm having trouble coming up with the boundary conditions.
Homework Equations
\bigtriangledown ^2 V = \frac{- \rho}{ \epsilon }
Uniqueness Thm: Knowing ρ and V at the surface means an answer I get satisfying Poisson's eq. and these conditions means it's the only one
Properties of grounded conductors: V=0 on surface (others?)
The Attempt at a Solution
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It's grounded, so I know V=0 along the entire surface of the sphere. I also thought I knew the charge density ρ since I have q within the volume V the sphere occupies. However, I'm thrown off by the statement "... and the charge on the sphere to satisfy the BCs". At first I assumed no charge on the surface but the line implies there should be some, so I think there must be some caveat of the setup I'm missing. If there is indeed charge on the sphere, does this affect ρ, since the sphere is infinitely thin I'm not sure if it would count as being 'within' the volume?
Griffiths does a similar problem, except with the charge outside of the sphere; I attempted to adapt his solution to mine by adding an image charge outside of the sphere to at least calculate V inside of the shell, but I can't see how to prove that it equals zero everywhere on the surface as he did (he cited some ancient ratio equation or something...)
Any tips? We just started doing things like this involving BCs with Laplace/Poisson's equation but this is my first exposure. I can't think of how the field/potential should behave either inside or outside because I can't decide how the charge, if there is any, affects my situation.