# Network Analysis for finding power delivered

We need to find the power delivered by the 5V source in the above network. I usually apply superposition theorem when I need to find the power delivered by a source when there are many power sources in the same circuit. But here I am not able to understand how to approach.

First, calculate the current through the 3 Ω and 2 Ω resistors by simple Ohm's law (I = V⁄R). The result is shown in the following figure (they are denoted by I1 and I2).

Next task is to calculate the current through the 5V source which is denoted by I3. We can use Kirchoff's Current Law (KCL) either at Network 1 or Network 2.

Lets say we apply KCL at Network 1. Here, we can write -

I2 + I3 = I1

Or,

I3 = I1 - I2

Or,

I3 = 2A - 1A = 1A

So, we have found the value of current through the voltage source is 1A. So, the supplied power by the voltage source is 5 × 1 = 5W.

• Wow, that's a much simple method. – John Cena Nov 28 '18 at 11:10
1. Since you know the voltage across each resistor, you can find the current through it.

2. Knowing that, you can use the cut-set form of KCL to find the current through the 5 V source.

3. Knowing the voltage and current through the source, you can find the power it delivers to (or absorbs from) the rest of the circuit.

• Oh. Thanks. So I need to use knowledge of Graph Theory here. Ok. – John Cena Nov 27 '18 at 22:50
• Most of the graph theory is only needed if you want to program a computer to find the necessary cut sets to fully analyze a circuit. To solve this problem you just need to know that if you draw a line that divides the circuit in two, the algebraic sum of currents across that line must be zero. More detail in an old answer of mine. – The Photon Nov 27 '18 at 22:55
• Ok. Thanks again. Is Deoser Kuh a good book for Circuit Analysis? Or I should use Hayt Kemmerly? – John Cena Nov 27 '18 at 23:21
• Chua, Desoer & Kuh is the one I learned from, but that was a long time ago. – The Photon Nov 27 '18 at 23:43
• I also read some chapters from it and I think now also its worth reading. – John Cena Nov 28 '18 at 0:11