# Node-voltage Method, some misconception?

by M. next
Tags: nodal analysis, node-voltage
 P: 406 Nodal analysis is exactly the same think as node-voltage method. And we can choose any node we want as a reference point (GND). See the example We have a four nodes in our circuit. I pick as a reference point (GND) node 4. So node 4 by de definition has a potential of 0 V. So we left with three nodes. but we know that voltage at node 1 is equal 9V. So we only has two unknown nodal voltages 2 and 3. Now we apply KCL to the nodes where the unknown voltages appears. For node 2 (I assume that all current flow out from the node) $$\frac{V2}{R2} + \frac{V2 - V1}{R1} + \frac{V2 - V3}{R3} = 0$$ And we notice that V1 = E1 = 10V Now we write KCL for node 3. $$\frac{V3 - V2}{R3} + \frac{V3 - V1}{R4} = 0$$ And now all we have to do is to solve for V2 and V3 http://www.wolframalpha.com/input/?i...-+9%29%2F9%3D0 V2 = 3V and V3 = Vth = 6V Attached Thumbnails