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Hi, :smile:Please take a see on this Google

by PainterGuy
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PainterGuy
#1
May4-11, 11:39 PM
PainterGuy's Avatar
P: 317
Hi,

Please take a see on this Google Doc:
https://docs.google.com/viewer?a=v&p...thkey=CPWM-YUI

Can you help me with the highlighted part please? I don't understand it. Perhaps you can use the Fig. 8.51 to help me.

I am trying to learn Branch-Current Analysis, Mesh Analysis, and Nodal Analysis. I get confused between these these. What advice or suggestion you can provide me to get hold of these ideas?

Any help is appreciated.

Cheers
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Zryn
#2
May5-11, 12:32 AM
PF Gold
P: 322
A supernode is where a source (current or voltage, either independent or dependent) exists in more than one mesh (mesh analysis) or between two node voltages (nodal analysis).

In the picture you linked, you can see that E is the only source between V1 and V2, so describing the current through that section of the circuit in terms of its resistance and voltage will be difficult for your nodal analysis.

Mathonweb offers a few worked examples to demonstrate Nodal Analysis and then Circuitspot & Solved Problems offer two good examples of dealing with supernodes with both independent and dependent sources that may help your studies.
I_am_learning
#3
May5-11, 09:52 PM
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P: 669
Actually, the concept of supernode isn't an extra theory needed to solve circuit using nodal analysis. We can do without it too. (And actually we can derive that theory!)
In the document you linked to assume the node of V1 and Node1 and Node of V2 as node 2. Assume the current that flows from Node 1 to Node 2 as I12 (which you don't know)

Write KCL at both of the nodes.
For node1.
Outgoing current = Incoming current
V1/(4) + (V1-V2)/(10) + I12 = 6
For node2.
V2/(2) + (V2-V1)/(10) + 4 = I12

Add those two equations
V1/(4) + V2/(2) + 4 = 6
And you get what they call a super node equation.
And you get one bonus equation,
V1-V2 = 12.

And using the two you can solve the circuit.
And to write supernode equation, simply do this
When there is only a voltage source present between two nodes, Consider both of the nodes as brothers, supernodes brothers.
Sum of the outgoing currents (from both of the nodes) = sum of incoming currents (to both of the nodes).

No-need to consider currents going from one node to the other nodes of the two supernodes

I hope that helps

PainterGuy
#4
May31-11, 09:03 AM
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P: 317
Hi, :smile:Please take a see on this Google

Hi,

First of all let me offer my apologies for not offering my thanks in timely manner. I'm sorry. But I always appreciate the help I receive.

I will continue from Zryn's statement:
supernode is where a source (current or voltage, either independent or dependent) exists in more than one mesh (mesh analysis) or between two node voltages (nodal analysis).
Zryn, haven't you mixed up the concept of supernode and supermesh here. My book deals them separately.

Mesh analysis and supermesh:
In mesh analysis we apply KVL. Voltage sources offer no problem and the same is true of current source when it exists ONLY in one mesh. As a side note, a mesh is a loop which does not contain any other loop within itself. The problem arises when the current source (independent or dependent) exists between two meshes. So, then to solve the circuit a supermesh is created by excluding the current source and any elements connected in series with it.

Nodal analysis and supernode:
In nodal analysis we use KCL. Therefore, the number of current sources and their placement does not offer problem and the same is true when the voltage source is connected between the reference node (at 0V) and the nonreference node; we simply set the voltage at the nonreference node equal to the voltage of the voltage source. The problem arises when the voltage source (independent or dependent) is connected between two two nonreference nodes. Then, to solve the circuit a supernode is formed by enclosing the voltage source between the two nonreference nodes and any element connected in parallel with it.

Please correct or modify the text above if you think I have missed on something important, so that I don't run into trouble while doing the problems. Thanks

Cheers
PainterGuy
#5
Jun3-11, 01:24 AM
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P: 317
Would someone please comment on my previous post above? Thanks

Cheers


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