Thevenin’s and Norton’s theorems are circuit simplification methods, applied to simplify complex linear circuits and making circuit analysis easy and fast. These theorems are proposed by Léon Charles Thévenin and E. L. Norton respectively. We can convert a Thevenin’s equivalent circuit to Norton’s and vice versa.

## Thevenin’s theorem

Thevenin’s theorem states that any linear network with several power sources, resistances and a variable load can be represented in a much simpler circuit containing a single voltage source (V_{TH}) in series with a resistance (R_{TH}) and the variable load, where V_{TH} is the open-circuit voltage at the terminals of the load and R_{TH} is the equivalent resistance measured across the terminals while independent sources are turned off.

## Norton’s theorem

**Norton’s theorem states that** a linear two-terminal circuit can be replaced by an equivalent circuit consisting of a current source I_{N }in parallel with a resistor R_{N}, where I_{N} is the short-circuit current through the terminals and R_{N} is the input or equivalent resistance at the terminals when the independent sources are turned off.

## Convert Thevenin’s equivalent to Norton’s equivalent circuit

Thevenin’s equivalent to Norton’s equivalent circuit by applying ohm’s law.

According to Ohm’s law: **V=I.R**

As we know, R_{TH} = R_{NO}

Therefore, all we need to do is find the Current source. Applying the Ohm’s law:

**I _{NO} = V_{TH}/R_{NO}**

### Example

Let’s find Norton’s equivalent for the following Thevenin’s equivalent circuit.

Norton’s current source **I _{NO} = V_{TH}/R_{NO}** = 20/4 = 5A

Norton’s equivalent circuit is as follows: