# Flux through a Cube - Why would flux be zero?

by limonysal
Tags: cube, flux
 P: 12 1. The problem statement, all variables and given/known data This is a three part problem. I have the first and third part down but I'm just wondering about the second part which is multiple choice. A cube has one corner at the origin and the opposite corner at the point (L,L,L). The sides of the cube are parallel to the coordinate planes. The electric field in and around the cube is given by E = <(a+bx), c>. (im using bold for vectors) Part A: Find the total electric flux $$\Phi$$E through the surface of the cube. Express your answer in terms of a, b, c, and L. $$\Phi$$E =bL^3 Part B: Notice that the flux through the cube does not depend on a or c. Equivalently, if we were to set b=0, so that the electric field becomes E = , then the flux through the cube would be zero. Why? a. E' does not generate any flux across any of the surfaces. b. The flux into one side of the cube is exactly canceled by the flux out of the opposite side. c. Both of the above statements are true. 2. Relevant equations $$\Phi$$E=$$\int$$over the surface E*dA= EA when the field is perpendicular 3. The attempt at a solution I feel like the flux might be canceled out but I'm not sure if it might be both or just one of th reasons.