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Capacitance of a System (Spherical Conducting Shells)

  1. May 2, 2012 #1
    1. The problem statement, all variables and given/known data
    A spherical conducting shell of radius 0.1 m has a free charge of -2 μC. It is surrounded by a concentric spherical conducting shell of radius 0.12 m carrying a free charge of -2 μC. Between the shells is a dielectric material of dielectric constant 10 εo. If the dielectric material is linear, what is the capacitance of the system?


    2. Relevant equations
    C=(Q/V)=4πεo(ab/a-b)


    3. The attempt at a solution

    I attempted the solution with only the above equation, I'm just not sure how to to include the dielectric constant in my answer. The instructions say that I should use one of Maxwell's Equations. How do I make the connections I need?
     
  2. jcsd
  3. May 2, 2012 #2
    Nvm, I feel that I have the kinks worked out.
     
  4. May 2, 2012 #3

    rude man

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    I was gonna say, the first thing is to ignore the bit about the -2μC charges!
     
  5. May 2, 2012 #4
    Bingo. Free charge didn't matter.
     
  6. May 2, 2012 #5

    rude man

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    It might have if the dielectric were nonlinear, but colleges don't pull stuff like that on you!
    (In that case, C would have to be defined as dq/dV instead of q/V, or "incremental capacitance" instead of just "capacitance". Many types of real-life capacitors do display some nonlinearity, matter of fact.
     
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