# Gaussian Surface

A Gaussian Surface is a closed surface which exhibits Gaussian symmetry.

**Gaussian Symmetry:** Guarantees that my surface (given by the normal vector $dS$) is

- always perpendicular to or parallel to $E$
- $E$ is always the same magnitude everywhere.

Danger

We have to look for symmetry for all charges, not just inside the gaussian surface.

##### 3 Types of Gaussian Surface

- Gaussian Sphere
- Gaussian Cylinder
- Pillbox shape (you can just use a cylinder, but a rectangular shape works as well, or any shape).
- Make sure the electric field is always perpendicular or parallel to the shape