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Nodal Analysis

  1. Jun 10, 2010 #1
    The question might be simple for you guys but the problem is that it is not for ME !!

    I have a circuit and I have to determine the node voltages by Nodal Analysis method.

    And the one which I learned was in cases when we had a current source, I could simply write the equations using KCL.

    But I am totally confused in such cases when I have a voltage source, and I have been asked to do the same (i.e calculate the nodal voltages).

    Please HELP OUT !!
  2. jcsd
  3. Jun 10, 2010 #2

    The Electrician

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    Gold Member

    If you post the circuit you're having trouble with, you will be more likely to get help.
  4. Jun 13, 2010 #3
    Look up 'supernodes'. Basically, the nodes on either end of the voltage source combine into a single node. If the nodes are, for example, A and B, and the voltage souce between them 12v, then:

    A - B = 12v (where A - B just means "the voltage difference between A and B")

    Since A and B are treated as a single node, your KCL equation for the 'supernode' will have to include current going in and out of both nodes.
  5. Jul 17, 2010 #4
    If there is just one voltage source, it is easy to choose one of its nodes (usualy the negative terminal) as the reference node. For an example, check out this:
    http://circuits.solved-problems.com/resistive-circuits/problem-1-11-solving-circuit-nodes-nodal-analysis/ [Broken]
    If there are more than one voltage source, you may have to use supernode. You can find an example http://circuits.solved-problems.com/resistive-circuits/nodal-analysis-6-node-circuit/" [Broken]
    Last edited by a moderator: May 4, 2017
  6. Jul 17, 2010 #5
    Depending on what your circuit looks like, you may also be able to do a source transformation of a voltage source in series with a resistor to a current source in parallel with a resistor.
  7. Jul 18, 2010 #6
    If you can do it with current source, then you can definitely do it with voltage source. Just simply use the ohm law to convert the voltage to the current. For example, I=V/R, if You have the KCL equation,then just replace I variable with V/R by using ohm law.
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