ThéveninNorton

Thevenin and Norton theorems are fundamental concepts in electrical circuit analysis that simplify complex linear circuits into equivalent simpler forms. They are particularly useful for analyzing the behavior of a circuit with respect to a specific load.

Thevenin's theorem 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 resistor. This equivalent voltage source, known as the Thevenin voltage (Vth), is the open-circuit voltage across the two terminals. The equivalent resistor, known as the Thevenin resistance (Rth), is the equivalent resistance seen from the terminals with all independent sources turned off (voltage sources shorted, current sources opened).

Norton's theorem is very similar, but it proposes an equivalent circuit consisting of a single current source in parallel with a single resistor. This equivalent current source, the Norton current (In), is the short-circuit current flowing through the two terminals. The Norton resistance (Rn) is the same as the Thevenin resistance (Rth), calculated in the same way. The relationship between the two theorems is straightforward: Vth = In * Rth (or Rn).

These theorems allow engineers to analyze the voltage and current at a specific part of a larger circuit without having to re-analyze the entire circuit each time. They are widely used in power electronics, control systems, and general circuit design.