## Node-voltage Method, some misconception??

The question is written upon it

Sorry bad drawing, the circuit is closed from the left hand side but not from the right hand side.
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 But I don't see any problem. We can choose any node we want as a reference point (GND).
 But the essential node must connect at least 3 appliances!! Here we have only two :/

## Node-voltage Method, some misconception??

But you can solve the circuit using nodal analysis without any "essential node".
And I still don't understand why you need "essential nodes"?

 What's nodal analysis? How does it differ from node-voltage method. Elaborate please. [I only learnt node-voltage method :p] If we are talking only node-voltage method, how in the world did the Doctor consider the node below a reference when it only connects two appliances[see figure]. That's my question.
 I just checked, and they mean the same. Yet again, this is against the rule.
 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
 Lots of thanks Jhony, now I get it..
 We always measure all the voltage respect to this common point (reference point), also known as a "ground" (GND). And we assume that GND have zero voltage. Look ta this examples Attached Thumbnails
 Thanks, that's very kind of you. You really were helpful

 Tags nodal analysis, node-voltage