Calculate flux through face of a cube

1. Sep 12, 2013

mindarson

1. The problem statement, all variables and given/known data

A point charge q is located at the corner of a cube with edges of length
L. Find the electric flux through the shaded face at y = L.

2. Relevant equations

Gauss's Law; flux = ∫E$\bullet$n dA = qenc

3. The attempt at a solution

Here's what I'm thinking. In the problem statement, the charge q is located at a corner of the cube. I can't use Gauss's Law, due to lack of symmetry. However, I can draw a bigger cube instead, whose center is at the location of the charge. Then I have symmetry to use Gauss's law and say that the flux through the whole cube is q/ε. The face whose flux the problem wants me to calculate is now just 1/24 of the surface area of the whole (bigger) cube. Therefore I can say that the flux through the original face is just q/(24ε).

Is this correct, or am I just trying to be too clever by half, as they say?

Last edited: Sep 12, 2013
2. Sep 12, 2013

Tsunoyukami

This is correct and in fact is the manner in which the problem is solved in the solution manual. Good job!

3. Sep 12, 2013

mindarson

Nice! Seemed a bit too good to be true. :)