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Capacitance of two spherical conductors

  1. Mar 2, 2005 #1
    Given that two spherical conductors of radii r1 and r2 are separated by
    x>>(both r), connected by a thin wire, and charged with 7 uC - how is the charge distributed between the spheres (no charge on wire)?

    I tried using charge density but:

    Qtot/A1+A2 = Q1/A1 + Q/A2 doesn't work by definition

    then maybe:

    C(dV) = Q for either sphere - but how do you find dV without knowing the charge on each first? However, I got the correct answers when I flukily got dV by using the total charge of the system (7uC) and the sum of the radii (r1+r2) and multiplying by C of each sphere. I don't understand why this worked though.
     
  2. jcsd
  3. Mar 2, 2005 #2

    dextercioby

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    Well,i don't follow your "proof".I would advise you to use the fact that the charges on the 2 spheres are distributed in such a way,as to insure equal electric potential for each sphere...

    Daniel.
     
  4. Mar 2, 2005 #3
    why do they have to have the same electric potential?
     
  5. Mar 3, 2005 #4

    dextercioby

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    Because if they didn't charge would be moving from one to another until they did.So better assume that they already do.

    Daniel.
     
  6. Mar 3, 2005 #5
    ok, I see. This means that the potential difference between them is 0 right? Also, would the potential of the system be V1 + V2?
     
  7. Mar 3, 2005 #6

    dextercioby

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    Yes to the first question...As for the second,you don't need that piece of information.

    Daniel.
     
  8. Mar 3, 2005 #7
    Ok, but what if I wanted to know the potential of the system - would it be V1 + V2?
     
  9. Mar 4, 2005 #8

    dextercioby

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    Yes,potential (electric) is additive.But,again,you don't need this info.

    Daniel.
     
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