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Flux through a square

  1. Feb 16, 2009 #1
    1. The problem statement, all variables and given/known data

    The flux through a square plate, area 1 m^2, inclined at at an angle of 30 degrees to a field of strength of 100 N/C is

    ------\------->
    -------\------->
    --------\------->
    ---------\------->


    2. Relevant equations

    Flux=EACos(degree)


    3. The attempt at a solution

    = (100 N/C) (1m^2) Cos (60)
    95 Nm^2/C (not one of the options)
     
  2. jcsd
  3. Feb 16, 2009 #2

    LowlyPion

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    Homework Helper

    Cos 30 = .866
     
  4. Feb 17, 2009 #3
    O.k so i wouldn't do the angle perpendicular? So i put in cos (30)

    30 \
    --------\---------->
    ---------\---------->
    ----------\---------->
    -----------\---------->

    sorry don't know if the 30 degrees being there matters. When i put in the cos (30) i didn't get that ( does my calculator need to be in degrees ? ) O.k Thanx for any help. Also once i put the 100 N/C * 1m^2* Cos(30) i get 86.6 which is one of the options . Thank you
     
  5. Feb 17, 2009 #4

    LowlyPion

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    Degrees, not radians.

    You can always figure the correct values for 30 degrees and 45.

    A 45 degree angle means the sides are equal and hence sin or cos by Pythagoras of 45 is √2/2

    For 30 degrees, sin 30 is 1/2 (the side opposite is 1/2 the hypotenuse) and hence the cos 30 must be √3/2.
     
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