An ideal voltage source is a theoretical concept used to simplify circuit analysis. It is defined by having two main characteristics: it maintains a constant voltage regardless of the current drawn from it, and it has an internal resistance of zero. This means that the output voltage of the ideal voltage source does not drop, even when supplying current to a load. Since internal resistance limits the current flow and causes a voltage drop within real-world sources, an ideal voltage source must have an internal resistance of: