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Homework Help: Node Voltage help

  1. Sep 16, 2005 #1
    Can anyone help me find node-voltage equations for this circuit. The 10V power source is throwing me. Thanks.

    Attached Files:

  2. jcsd
  3. Sep 16, 2005 #2


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    Staff Emeritus
    Science Advisor

    Taking the - terminal of the 20V source as reference, or ground, the node above the 20 V source is +20 V above ground.

    The node just above the 10 V source is -10V with respect to ground, i.e. the negative terminal of the 20V source.
  4. Sep 16, 2005 #3
    I have this much
    Node 1: between the 25k resistor and the 11mA source)
    node 2: between the 500 ohm resitor, 10v source, 1k resistor and 500 resistor and the 11mA source
    V1: voltage across the 250 resistor
    V2: voltage arcross the 1k resistor
    reference node at the bottom of the pic
    node1: (V1-20)/25K+V1/250+.011+(V1-V2)/500=0
    node2: -.011+V2/1000+(V1-V2)/500+......=0

    I'm not quite sure how to hande the 10v supply.
    Last edited: Sep 16, 2005
  5. Sep 16, 2005 #4
  6. Sep 16, 2005 #5


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    Staff: Mentor

    There's only one unknown -- the voltage V1. Call the bottom rail ground, then you only have to solve for V1 to know all the voltages and currents in the circuit. The V2 is just -10V, set by the voltage source on the right.

    The answer for V1 is a nice round number (hint), and you can check your work by using that answer to figure out the 3 unknown currents flowing in/out of the V1 node. They should sum to zero, or you didn't solve your node 1 equation above correctly.

    Post the answer!
  7. Sep 22, 2005 #6
    its so easy and so basic...my professor gives us too complicated circuits..
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