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Homework Help: Net electric flux help?

  1. May 8, 2013 #1
    1. The problem statement, all variables and given/known data
    The charge distribution in the figure to the right is a cylindrical solid of charge q, radius R, and length H. The Gaussian surface S is a cylindrical shell with radius r and length h, with r > R. Determine the net electric flux given that q = 12Q, R = 5L, H = 6L, r does not apply, and h = 3L (type the integer value, along with the sign, without typing units Q/e0):

    2. Relevant equations
    "The net electric flux will be in units of Q/e0, with e0 the permittivity of free space."

    3. The attempt at a solution
    have no idea how to do this. I tried q/e0 = 12/(8.85x10^-12) but its too huge value..maybe i got the wrong equation.

    edit; i just got this. turns out you didn't need ANY equations at all, just common sense. its just q*(h/H) which in this case is 6 though I have no idea why this is the answer, it would just give you the enclosed charge right? you would still have to divide by e0..?
    Last edited: May 8, 2013
  2. jcsd
  3. May 8, 2013 #2

    rude man

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    Homework Helper
    Gold Member

    Yes the net charge inside the Gaussian surface is qh/H but substitute q = 12Q and then ε0*(electric flux) = qh/H. The answer thus is electric flux = 12Qh/Hε0 but the answer is to be in units of Q/ε0 so what is the answer then? Does it help if I rewrite flux = (12h/H)(Q/ε0)?
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