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Homework Help: Electric Field in Coaxial Cable

  1. Jun 24, 2007 #1
    1. The problem statement, all variables and given/known data
    a=radius of inner electrode = 0.05 cm
    b=radius of outer electrode = 0.5 cm
    Vo = 130 V

    QUESTION: What is the electric field at surface of the inner electrode in units of V/m?
    2. Relevant equations
    Given equations
    Potential at radius r b/w inner&outer electrodes is
    V=Vo*ln(r/a) (Eq 1)

    Elect field at r is
    E(V/m) = (1/r)*[V/ln(b/a)] Eq (2)

    3. The attempt at a solution

    First in finding the V at surface of inner electrode,
    the value of r is same as a because it's at surface, so the ln (r/a) term
    becomes zero. So that is where I am stuck. Are the equations I am given correct?
  2. jcsd
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