De stelling van Thévenin

Thevenin's theorem states that any linear two-terminal circuit can be replaced by an equivalent circuit with a single voltage source in series with a resistor.

In the absence of load, the voltage across the open terminals will be the Thévenin voltage.

For finding Thévenin resistance, all independent sources are turned off. Then the resistance seen across the terminals is the Thévenin resistance.

If the circuit contains dependent sources, the independent sources are still switched off, but a known test source is applied at the terminals.

From the resulting terminal voltage or current, the Thévenin resistance can be determined.

Finally, the load is connected to the equivalent circuit. The current through the load is calculated using the current divider formula. Using Ohm's Law, the Thévenin voltage across the load is determined.

A battery can be represented as the Thévenin equivalent circuit. Thévenin voltage is the battery's open circuit voltage and resistance is its internal resistance.

Knowing the Thévenin parameters, it is easy to calculate the current for various loads without re-examining the entire circuit.