The original circuit
Calculating the equivalent output voltage
Calculating the equivalent resistance
The equivalent circuit

Thevenin's theorem for electrical networks states that any combination of voltage sources and resistors with two terminals is electrically equivalent to a single voltage source V and a single series resistor R. For single frequency AC systems the theorem can also be applied to general impedances, not just resistors. Wikipedia does not have an article with this exact name. ... Wikipedia does not have an article with this exact name. ... Wikipedia does not have an article with this exact name. ... Wikipedia does not have an article with this exact name. ... An electrical network or electrical circuit is an interconnection of electrical elements such as resistors, inductors, capacitors, diodes, switches and transistors. ... In the physical sciences, potential difference is the difference in potential between two points in a conservative vector field. ... Resistor symbols A resistor is a two-terminal electrical component that creates an electrical potential difference across its terminals that is proportional to the current passing through it. ... In electrical engineering, impedance is, loosely speaking, a measure of resistance to a sinusoidal electric current. ...

The theorem was first discovered by German scientist Hermann von Helmholtz in 1853, but was then rediscovered in 1883 by French telegraph engineer Léon Charles Thévenin (1857-1926). Hermann von Helmholtz Hermann Ludwig Ferdinand von Helmholtz (August 31, 1821 – September 8, 1894) was a German physician and physicist. ... Leon Charles Thevenin (March 30, 1857- September 21, 1926) was born in Meaux, France. ... 1857 was a common year starting on Thursday (see link for calendar). ... 1926 was a common year starting on Friday (link will take you to calendar). ...

To calculate the equivalent circuit:

1. Remove the load circuit.
2. Calculate the voltage, V, at the output from the original sources.
3. Now replace voltage sources with shorts and current sources with open circuits.
4. Replace the load circuit with an imaginary ohm meter and measure the total resistance, R, looking back into the circuit, with the sources removed.
5. The equivalent circuit is a voltage source with voltage V in series with a resistance R in series with the load.

The Thevenin-equivalent voltage is the voltage at the output terminals of the original circuit. When calculating a Thevenin-equivalent voltage, the voltage divider principle is often useful, by declaring one terminal to be V_out and the other terminal to be at the ground point. In the example, In electronics, a voltage divider or resistor divider is a design technique used to create a voltage (Vout) which is proportional to another voltage (Vin). ...

The Thevenin-equivalent resistance is the resistance measured across points A and B "looking back" into the circuit. It is important to first replace all voltage- and current-sources with their internal resistances. For an ideal voltage source, this means replace the voltage source with a short circuit. For an ideal current source, this means replace the current source with an open circuit. Resistance can then be calculated across the terminals using the formulae for series and parallel circuits. In the example, Left: Series / Right: Parallel Arrows indicate direction of current flow. ...

See also

• Norton's theorem
• Impedance
• Superposition
• Node analysis
• Mesh analysis

Nortons theorem for electrical networks states that any collection of voltage sources and resistors with two terminals is electrically equivalent to an ideal current source I in parallel with a single resistor R. The theorem can also be applied to general impedances, not just resistors. ... In electrical engineering, impedance is, loosely speaking, a measure of resistance to a sinusoidal electric current. ... The term superposition can have several meanings: Quantum superposition Law of superposition in geology and archaeology Superposition principle for vector fields Superposition Calculus is used for equational first-order reasoning This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ...

External links

• Origins of the equivalent circuit concept
• Thevenin's theorem at allaboutcircuits.com