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Need help finding the electric potential

  1. Nov 5, 2011 #1
    1. The problem statement, all variables and given/known data

    calculate the electric potential for the following:

    A cylindrical cable with a center rod of diameter a surrounded by a gap and a
    thick pipe with inner and outer radii b & c. The charge distribution on the inner rod
    is ρ = k cos(sπ/2a), and the outer rod has a uniform charge density such that the total
    system is neutral.

    2. Relevant equations

    V=-integral E.dl
    gausses law


    3. The attempt at a solution

    i calculated the electric field everywhere, but im not sure how to go about calculating V.

    My best guess is to calculate V the cylinder, setting my reference point at infinity and then work my way inside the cylinder, calculating V in each region.

    But since the total system is neutral, the integral gives V=0 for outside the cylinder, which I have a feeling is incorrect...

    My book doesn't really have any examples or explanations for charge distributions of this type so I just wanted to know if im on the right track.
     
    Last edited: Nov 5, 2011
  2. jcsd
  3. Nov 5, 2011 #2

    Simon Bridge

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    this is sort of a cylindrical capacitor isn't it?
    https://www.physicsforums.com/showthread.php?t=246762

    The key is to use cylindrical coordinates.
    Notice that the field depends only on radius.
    Choose cylindrical gaussian surfaces.

    Some people find the differential form more useful.
     
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