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Homework Help: Flux through a square surface

  1. Sep 2, 2011 #1
    1. The problem statement, all variables and given/known data

    A square surface, 34 mm each side, is immersed with an electric field of magnitude 1700 N/C. The field lines make a 35 degree angle with the normal line. Find the electric flux through the surface.

    2. Relevant equations

    [itex]\oint[/itex]E[itex]\cdot[/itex]dA

    3. The attempt at a solution

    Well, since E[itex]\cdot[/itex]dA can be rewritten as EA*cos([itex]\Theta[/itex]), I did that, and since E and Cos([itex]\Theta[/itex]) are constants, I pulled them out of the integral giving me

    E*Cos([itex]\Theta[/itex])[itex]\oint[/itex]dA

    which comes out to be E*Cos([itex]\Theta[/itex])*A, but when I plug in 1700*Cos(35)*.0034[itex]^{2}[/itex] it's wrong.

    Any suggestions?
     
  2. jcsd
  3. Sep 2, 2011 #2

    vela

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    You've converted mm to m incorrectly.
     
  4. Sep 2, 2011 #3
    Sorry, that's a typo on my part, it's supposed to be 3.4 mm
     
  5. Sep 2, 2011 #4

    vela

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    Is your calculator in degree mode? Your method is correct.
     
  6. Sep 2, 2011 #5
    Yeah, it is. Must be webassign, I hate it. Thanks very much for your help.
     
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