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Homework Help: Gauss's law, cylinder of length L

  1. Feb 13, 2010 #1
    http://img404.imageshack.us/img404/4148/gauss3j.png [Broken] (infinitly long)

    [itex]\Phi=\Phi_{0}(1-{r \over R}) {C \over m^2}[/itex]

    What's the charge of the cylinder of length L?

    Again, almost everything was wrong...
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Feb 13, 2010 #2
    anyone? :(
  4. Feb 14, 2010 #3
    Here's link to my paper: http://img202.imageshack.us/img202/5889/physics.jpg [Broken]
    Last edited by a moderator: May 4, 2017
  5. Feb 14, 2010 #4
    You need to be much clearer in the problem statement and your work.

    Is the cylinder hollow? What do r, R, [tex]\Phi[/tex], and [tex]\Phi_0[/tex] represent?

    Also, it's probably OK to write notes in your homework like "the electric field points radially outward so the flux through the top and bottom of the gaussian cylinder is zero" rather than relying on vague drawings
  6. Feb 14, 2010 #5
    This is from the test, as you can see, and everything I knew was written down...
  7. Feb 14, 2010 #6
    please delete this post
  8. Feb 14, 2010 #7
    ok, now I got the following:

    Q=integral of /rho(1-r/R) times rdr d/phi dl

    Which is the answer for the question of what's the charge of the cylinder L.

    How to calculate it?
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