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Homework Help: Two wires in parallel and capacitence

  1. Oct 8, 2006 #1
    I have to show that the capacitance per unit length for two identical wires of radius d separated (at the center) a distance D as:

    C/l = (pi epsilon0) / ( ln [( D - d ) / d]

    And I'm clueless. How do I go about solving this?

    I started by trying with C = q / V to C = lambda * l / V .. but I didn't get far as I didn't know what to do with lambda.

    Edit: they are oppositely charged, and the charge is distributed evenly along the surface of each wire.
     
  2. jcsd
  3. Oct 11, 2006 #2

    Meir Achuz

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    Calculate the potential difference V between the two wires
    using phi=2\lambda ln(r/d) (in Gaussian units) for each wire.
    Then C/l=\lambda/V
     
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