ok the question is....A point charge of 8.00 nC is at the center of a cube with sides that are 0.200 m. What is the electric flux through (a) the surface of the cube, (b) one of the six faces of the cube?

Question

ok so would I just use Gauss's law 4* pi*k*q? even though that is spherical? I am confused on how to determine what equation to use for the whole surface and for just one side

Answer 1

(2) Yes, use Gauss' law. It is good for any closed surface shape surrounding a charge, and does not depend upon the location of the charge!

In your case, since the charge is in the center, just divide by six to get the flux through one side, because of the symmetry of the cube and the charge's location.

Answer 2

ok so the length of the sides doesn't matter in this case? I am confused! haha

Answer 3

Yes, the cube length does not matter for the FLUX. The E-field will decrease for larger cubes, but the area increase will cancel it out.