Norton's Method / Theorem

As you can easily notice from the drawing itself, this method is very similar to Thevenin's method, the only significant difference is that we replace the circuit with a current source (in Thevenin's method it was a voltage source) and the impedance is connected in parallel instead of series.

In the overwhelming majority of cases it doesn't matter which of these two methods we use.

Content of Norton's theorem:

A stationary, linear, and lumped electric circuit can be replaced by a circuit consisting of an ideal current source (Norton source) and an impedance (resistor in DC circuits).

Steps of the method:

1. We remove the branch from the circuit for which we want to calculate the current
2. For the rest of the circuit, we calculate:
   1. Norton source current
   2. Equivalent impedance (compare -> equivalent resistance)
3. We connect these elements to the analyzed branch and calculate the current in that branch