Why is the net flux in a cube surface area zero when the source charge is located outside? Can some one please explain why a charge located outside a box shaped surface area produces zero net flux? I know this question has been asked many times, but I can't seem to find one that answers my problem with it.
I cannot seem to make sense of this because if the electric field decreases in magnitude with increasing distance from the source, won't the electric field lines leaving the surface have less magnitude than the ones entering it since it is farther from the source due to the surface area having a certain width, which leads to a greater flux inwards than outwards? Thanks﻿ in advance.
 A: I think I understand your confusion. The field lines that you see in illustrations of flux do not get weaker over time, counterintuitively. The 1/r^2 dropoff of an electric field is not due to the lines getting weaker; it is due to the fact that the electric field is being spread over a wider area as it gets further from the source charge, and thus it is less dense. In other words, that 1/r^2 isn't a property of the field- it's a property of geometry. Each line you see entering a closed surface, like a box, is the same strength when entering as it is when exiting.
Hope that helps!
A: Just visualize the flux as an incompressible  fluid flow (that's what the word means after all) and where the charge is a magical source of fluid. Now imagine a  box-shaped region in  the fluid. Because the fluid is incompressible the total amount of fluid in the box must  always stay the same. If you have a charge (source) inside   of then box then whatever fluid is appearing at the source must flow out of the box: there is a net flux. If the source is outside the box then whatever flows in through some sides  of the box must flow out somewhere else. In this case the net flux is zero. 
A: Remember that for the flux calculation, there is a scalar product and the angle between the surface normal and the field at each point must be involved. The larger the angle, the smaller the flux.
If the surface is farther, the field is weaker but the angle is also lower. On the whole cube, the flux compensate each other.
A: If you placed any net charge outside the box (for a uniform electric field), the net flux through it is zero. Why? Because what we mean by a uniform electric field is a series of parallel field lines passing in and out of the box. 
Uniform electric fields are generated in capacitor plates. The inverse square law would say that the field lines would diverge and you might think that this creates a non-zero flux, but at appropriate distances (in millimetres probably) that divergence would be minimum and we can imagine those field lines to be uniform as they are called. 
What I mean by divergence of field lines is literally the spreading of theirs.
