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Homework Help: Energy of Coaxial Cylindrical Shells

  1. Sep 27, 2010 #1
    1. The problem statement, all variables and given/known data

    Calculate the energy per unit length for two long coaxial cylindrical shells, neglecting end effects. The inner and outer cylinders have radii a and b, and linear charge densities λ and -λ, uniformly distributed on the surface, respectively.

    2. The attempt at a solution

    Alright so first thing I did was calculate the electric field in various regions using Gauss' Law:
    i) for r<a E=0
    ii) for a<r<b [tex] E=\frac{\lambda}{2\pi \epsilon r} [/tex]
    iii) for r>b E=0

    Now I'm not too sure how to find the energy per unit length: we have the formula [tex] E=1/2 \int \lambda V \ dl [/tex] so should I just find the potential V(r) then sub it into that equation?
    I can find V(r) by [tex] \int E \ dl [/tex]
  2. jcsd
  3. Sep 29, 2010 #2
    Haha Phys 400? Im having similar trouble...
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