This simulation shows a simplified version of Gauss' law as applied to a square "surface" (more accurately, it's a cylinder with a square cross section). The green vectors show the electric field at several locations along the surface.[br][br]Move the surface by dragging. The four charges (really, lines of charge) can also be moved by dragging, and their charge can be adjusted with the sliders. Set a slider to zero to hide the charge.

[list=1][*]Under what circumstances is the net flux zero? Positive? Negative?[/*][*]Does the location of the charges that are inside the surface affect the net flux?[/*][*]Does the location of the charges that are outside the surface affect the net flux?[/*][*]Does the sum of the charge inside the surface affect the net flux?[/*][*]Does the sum of the charge outside the surface affect the net flux?[/*][/list]