Theveninsoviteyhtälöä

Theveninsoviteyhtälöä, often referred to as Thevenin's theorem in English, is a fundamental concept in electrical engineering used for simplifying complex linear electrical circuits. It states that any linear electrical network with two terminals can be replaced by an equivalent circuit consisting of a single voltage source in series with a single resistance. This equivalent circuit behaves identically to the original network with respect to the two terminals.

The equivalent voltage source, known as the Thevenin voltage ($V_{th}$), is equal to the open-circuit voltage across the two terminals of the original network. The equivalent resistance, called the Thevenin resistance ($R_{th}$), is the resistance seen looking into the network from the two terminals when all independent sources are turned off (voltage sources are replaced by short circuits, and current sources by open circuits).

Thevenin's theorem is particularly useful for analyzing the behavior of a circuit when a load is connected to a complex network. Instead of recalculating the entire circuit each time the load changes, one can first determine the Thevenin equivalent of the network and then analyze the simple series circuit formed by $V_{th}$, $R_{th}$, and the load. This significantly simplifies calculations and provides a clear understanding of how different loads will affect the circuit's performance. It is a powerful tool for circuit analysis and design.