I'm not sure when and when you can't use Gauss' Law.
If I have the situation given in the first figure, where the red circle and the blue circle both represent 2 different Gaussian Surfaces. If I wanted to find the Electric Field at point (2,0). If use the red Gaussian Surface I find that
However, if I use the blue Gaussian surface to calculate the electric field at (2,0), I get E = 0 because there is no charge enclosed inside the blue Gaussian Surface.
I know that there is an electric field at that point, how do I reconcile this?
Question 2: If I have the situation given by the figure below:
(Charge +Q is at (0,0.5) and Charge -Q is at (0,-0.5))
If I use Gauss' Law to calculate the electric field at Point A, I get that E = 0 (because the total charge contained within the Gaussian Surface is 0).
However, if I calculate it by calculating the net electric field using the equation:
E = k *[-Q/(2.5)^2 + Q/(1.5)^2] = k * 64*Q/225
I know I am using Gauss's Law incorrectly somehow in both of these instances but I am not sure how either cause is incorrect.
Help is really appreciated! Thank you!