> [!significance] Metadata > Author:: [Vatsal Sanjay](https://vatsalsanjay.com)<br> > Date published:: Jan 21, 2025<br> > Date modified:: Jan 21, 2025 at 11:03 CET # Gaussian surface is very similar to the control volume in fluid mechanics They are closely related in a mathematical sense. In [[Gauss law of Electrostatics|Gauss’s law for electrostatics]], one picks a closed surface—the Gaussian surface—to evaluate the net electric flux and relate it to enclosed charge via the divergence theorem. In fluid mechanics, one defines a control volume (with a control surface) to analyze fluxes of mass, momentum, or energy. Both rely on the same underlying integral theorem (the divergence theorem) to connect fluxes through the surface to sources or sinks within the volume. The physical interpretations differ—charge density for electromagnetism versus mass or momentum for fluid flow—but the conceptual framework is very similar.