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Homework Help: Flux through each face on a cube

  1. Apr 7, 2009 #1
    1. The problem statement, all variables and given/known data

    A point charge q is placed at one corner of a cube of edge a. What is the flux through each of the cube faces?

    2. Relevant equations

    3. The attempt at a solution

    I drew a diagram of the situation. I'm pretty sure that I should use Gauss' Law and some symmetry arguments but I am not sure how to integrate over the cubes faces taking into account that the electric field produced by the point charge is radially outwards, like a sphere cutting through the face of the cube ( poorly described I know, sorry).

    Thanks for the help.
  2. jcsd
  3. Apr 7, 2009 #2
    By Gauss's Law, the flux through the whole cube is just [tex] 6q/\epsilon_0 [/tex]. Now, apply a simple symmetry argument to get the answer.
  4. May 4, 2009 #3
    I'm not sure why is it 6q ? If there is only one charge of magnitude 1q surely the flux is

  5. May 4, 2009 #4

    Doc Al

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    Staff: Mentor

    Right: The total flux from that charge is just q/ε0. So what's the total flux through the cube? Through each face of the cube? (No integration needed, just symmetry.)
  6. May 4, 2009 #5
    Ah right I see now. Thanks very much, was thinking about this completely the wrong way.
  7. May 6, 2009 #6
    What is the answer you are getting?
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