Superposition

Superposition is a good method to apply in analyzing circuits with multiple sources. The basic concept of this method is to analyze a circuit one source at a time. Using the Superposition Theorem, we remove all the independent sources, except one, and analyze that circuit for that one. Then we repeat the procedure for another source, and so on. Finally, the net result is found by summing all the single -source results. 

'Removing' Power Sources

If we have two voltage sources and we were to remove one source, and still have a complete circuit, we must replace the voltage source with a short circuit.

Similarly, if we gave two current sources and we were to remove one source, we must replace the current source with an open circuit.

Example:

Find the voltage at node B in the circuit below:

We can remove the 10V source and find the node voltage B using KCL:

Next, we remove the 3V source and find node voltage B using KCL:

Finally, we can add the results we got from these two calculations. 

The node voltage B is (9/11)+(-20/11)= -1V

This would also be the result if we use other methods such as Source Transformation, Mesh and Nodal analysis.

The Superposition Method does not only work for computing voltages, but also for computing currents.

Source:

University of Texas at Austin