> [!summary] Gaussian surfaces are imaginary closed surfaces used for Gauss's Law. >[!info]+ Read Time **⏱ 1 min** # Definition Gaussian surfaces are a type of imaginary closed surface used for [[Gauss's Law|Gauss's law]]. They are useful for the Gauss law as they act as a closed surface to calculate flux coming in or out of. In Gauss' Law, when you pick a Gaussian surface, you integrate over the whole closed surface looking at the electric field at each point, or you make some symmetry argument and describe it as a 3D surface. There are different types of imaginary surfaces; the choice depends on the symmetry of a problem. | Surface | Best For | Symmetry | Field Direction | E Constant? | Example | | -------- | ------------------------ | ----------- | --------------- | --------------- | ----------------- | | Sphere | Point/spherical charge | Spherical | Radial | Yes | Point charge | | Cylinder | Infinite line of charge | Cylindrical | Radial for axis | Yes (side only) | Long charged wire | | Disk | Infinite plane of charge | Planar | Perpendicular | Yes | Charged sheet | --- > 💡 Found this concept helpful? [Star Math & Matter on GitHub](https://github.com/rajeevphysics/Obsidian-MathMatter) to support more intuitive science breakdowns like this. ---