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Homework Help: Electric Potential in a Conductor

  1. Sep 29, 2005 #1
    #1. We have a hollow metal spherical shell with charge -q and with radius rb
    #2. We have a soild metal sphere supported by an insulating stand with charge +q and radius rb
    #3. The solid metal sphere is located in the center of the hollow metal spherical shell (aka. #2 is in #1)
    The question asks me to calculate the potential, V(r) when:
    A. r < ra
    B. ra < r < rb
    C. r > rb

    The solution:

    A. k*[(q/ ra)-(q/ rb)] where k= 1/(4*pi*epsilon_0)

    C. k*[(q/r)-(q/r)] = 0

    What I don’t understand:

    A. The electric field in #2 is 0; hence the electric potential should be constant. So, I would think that the potential of r < ra should be V=k*(q/ ra) because it is telling us to find the potential inside of ra which should be a constant throughout the solid sphere. Right? Then how come the answer gives me the sum of the electric potential for #1 and #2??

    C. I got totally lost at part C any clue please?
    Last edited: Sep 29, 2005
  2. jcsd
  3. Sep 29, 2005 #2


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    Homework Helper

    what is your understanding of potential, please.(you are online)
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