1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook