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Homework Help: Electric Field due to a charged conducting finite cylindrical shell.

  1. Apr 30, 2008 #1
    Hi everyone. I'm having a bit of trouble with finding an electric field. Basically, I'm trying to understand the formula for a cylindrical capacitor, so the method involves integrating the field between two conducting cylindrical shells. Firstly can Gauss's law be used in this case, because the cylinder is finite? Are the field lines all radial, even at the very end of the cylinder? If so, this leads to my next problem. The field turns out to be:
    So, when you integrate this to obtain the potential, you will end up with a natural logarithm, meaning at infinity, the potential is infinity!? I'm sure this is wrong but I just can't see where the error is. Any help would be greatly appreciated!
  2. jcsd
  3. Apr 30, 2008 #2
    The Gauss theorem CANNOT be used for finite charged cylinder.
  4. May 1, 2008 #3
    Ok then, but how can you calculate the field inbetween the two finite cylinders? You need the field so you can integrate it to get the potential, which you can then use to calculate the capacitance, which, I'm told, turns out to be
    C=(2*Pi*epsilon_0*Length)/log((second radius)/(first radius))
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