# Electric flux question

1. Sep 8, 2009

### bitrex

Electric flux question (solved it)

1. The problem statement, all variables and given/known data
I have to find the flux of $$F = ix + jy + kz$$ 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 $$zb^2$$. Similarly the flux through the other 2 surfaces should be $$xb^2$$ and $$yb^2$$. 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 $$\iint \vec{E}\cdot \vec{n} dA$$ the normal vector to say, the x y plane is going to be $$i0 + j0 + k$$ and the field on the xy plane is going to be $$ix + jy +k0$$. 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