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Homework Help: 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

    User Avatar
    Science Advisor
    Homework Helper

    this is sort of a cylindrical capacitor isn't it?

    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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