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Homework Help: Electric field in a hollow cylinder

  1. Oct 29, 2011 #1
    An infinitely long thick hollow cylinder has inner radius Rin and outer radius Rout. It has a non-uniform volume charge density, ρ(r) = ρ0r/Rout where r is the distance from the cylinder axis. What is the electric field magnitude as a function of r, for Rin < r < Rout?

    for this problem, when you find qinside, do you integrate from Rin to r or from Rin to Rout? i'm confused because i would have expected it to be the latter, but in the solutions they integrate from Rin to r. can someone please explain this?

    also, if you try to find the e-field where r > Rout, do you integrate from r to Rout?

    Solution is here (problem II):
    http://www.physics.gatech.edu/~em92/Classes/Fall2011/2212GHJ/main/quiz_help/200908/q2s.pdf
     
    Last edited by a moderator: Apr 26, 2017
  2. jcsd
  3. Oct 30, 2011 #2

    rude man

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    Just use Gauss' theorem. The surface has radius r, and
    q(inside) is whatever's inside!
     
  4. Oct 30, 2011 #3
    since in the example in the document it asks for Rin < r < Rout.. why does it integrate from Rout to r??
     
  5. Oct 30, 2011 #4

    rude man

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    It doesn't. It integrates from Rin to r.
     
  6. Oct 30, 2011 #5
    but why not Rin to Rout?
     
  7. Oct 30, 2011 #6

    rude man

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    Because ity asks for the field at Rin < r < Rout, not AT Rout.
     
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