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Different voltages on the same node?

  1. Dec 10, 2015 #1
    In this picture: http://imgur.com/lfNiDjL

    I see that at node A, the voltage is 10V since it is connected to the independent voltage source. But node A is also connected to the dependent voltage source 10Io.

    If I do KVL on the left loop, Io comes out to be 0.2A. Plugging this into the dependent source, the dependent source is at 2V. How is this possible?

    The dependent source says Node A is at 10V. But the dependent source says Node A is at 2V. Since both sourcers are connected at the same point, they should be at the same voltages, right?

    Which voltage is correct? How am I analyzing this incorrectly?
  2. jcsd
  3. Dec 10, 2015 #2


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    10V at node A, period. That fixes the current through R1, which determines the voltage across the dependent source, which is referenced to node A. The dependent source is 10V on the left side and 12V on the right since there is 2V across it.
  4. Dec 10, 2015 #3


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    A single node cannot have a "voltage".
    A voltage always is the potential DIFFERENCE between two nodes.
    Only in case one node is grounded we speak about a "node voltage" - without mentioning that this automatically means: Referenced to the grounded node.
  5. Dec 10, 2015 #4


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    That is 10V wrt the bottom end of R1.

    That is 2V wrt the node between the dependent source and R2.

    So they need not be inconsistent.

    Mark these voltages on the drawing and apply KVL to the right hand loop.
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