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Homework Help: Electric flux through a plane described by an equation

  1. Feb 4, 2013 #1
    1. The problem statement, all variables and given/known data

    The elctric field in a certain region of space has components Ex = 6.0 N/C, Ey = 7.0 N/C, and Ez = 0. Find the electric flux though the surface x = 6y, 0 < x < 6.0 m, 0 < z < 1.0 m. What is the angle between the electric field and the unit vector normal to the surface?


    2. Relevant equations

    Flux=E dot A

    3. The attempt at a solution

    Flux=(6N/C)(6m)(1m)= 36 Nm^2/C
    This is the same as the answer in the back of the book but it seems too easy, and I think there should be a cosine in there.
     
  2. jcsd
  3. Feb 4, 2013 #2
    You have [itex]\vec{E}(x, y, z)=(6.0, 7.0, 0) N/C[/itex].
    [itex]\Phi=\vec{E}(x, y, z)\bullet\vec{S}[/itex] where [itex]\vec{S}[/itex] is a vector area. You can use the magnitudes of the vectors and the angle between them as [itex]EScos\phi[/itex], where [itex]\phi[/itex] is the angle between the field lines and the normal to the the surface area [itex]S[/itex]. Do you know how to find the normal to the surface you have?
     
  4. Feb 4, 2013 #3
    Yes, I understand where the normal is, I just don't understand how to find the angle between the E-field lines and the area vector (normal). I can find the angle between the e-field lines and the x and y axis but I cannot find the angle of the plane.
     
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