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Homework Help: Finding magnitude of electric field of a cylinder

  1. Sep 2, 2012 #1
    1. The problem statement, all variables and given/known data

    2. Relevant equations
    E = 1/4([itex]\pi[/itex] [itex]\epsilon_{0}[/itex]) * [itex]\frac{p}{r^2}[/itex]

    3. The attempt at a solution
    E = 2[itex]\pi[/itex][itex]r_{0}[/itex] [itex]\epsilon_{0}[/itex] = pl/[itex]\epsilon_{0}[/itex]
    = [itex]\frac{pr}{2\pi r_{0} \epsilon_{0}}[/itex]

    I am going by what I know about Gauss Law and using a similar format for the Electric field equation for a infinite charge line in a cylinder.

    I fixed it little by little and I left off at:
    E = [itex]\frac{r}{2 \epsilon_{0}}[/itex]
    The hint it gives me is that i am missing p but putting p in the numerator or denominator will say it is not dependent on p.
    I probably did something wrong in the process or used a wrong equation.
  2. jcsd
  3. Sep 2, 2012 #2
    What you have written is gibberish. Is this a uniformly charged cylinder?

    You have to start at Gauss's law:

    [tex]\oint E \cdot dA = Q_\text{enc}/\epsilon_0[/tex]

    And then invoke cylindrical symmetry to say that

    [tex]|E|A = Q_\text{enc}/\epsilon_0[/tex]

    What is the area [itex]A[/itex] of the Gaussian surface? What is the charge enclosed by this surface?
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