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 question

  1. Sep 8, 2009 #1
    Electric flux question (solved it)

    1. The problem statement, all variables and given/known data
    I have to find the flux of [tex]F = ix + jy + kz[/tex] through three squares, each lying in the xy, xz, and zy planes with sides of length b.

    2. Relevant equations

    flux with planar symmetry - E*A.

    3. The attempt at a solution

    The flux through the square in the x y plane is going to be the z component of the flux function times the area, or [tex]zb^2[/tex]. Similarly the flux through the other 2 surfaces should be [tex]xb^2[/tex] and [tex]yb^2[/tex]. I would think I could sum these to get the total flux through the three surfaces, but the answer turns out to be 0. Ideas would be appreciated.

    Edit: The flux through the three squares is zero because they are all perpendicular to the field vector, that is with [tex]\iint \vec{E}\cdot \vec{n} dA[/tex] the normal vector to say, the x y plane is going to be [tex]i0 + j0 + k[/tex] and the field on the xy plane is going to be [tex]ix + jy +k0[/tex]. Same for the other planes. So there's no total flux through the planes because they're always perpendicular to the field vector. No point in doing the integral!
    Last edited: Sep 8, 2009
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted