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Homework Help: Find the voltage at point X on the circuit

  1. Jan 15, 2010 #1
    1. The problem statement, all variables and given/known data

    Here is the circuit:

    I have found I1 to be -39.23A, I2 to be -25.38A, but I'm having difficulty reasoning how to find the voltage of point X.

    3. The attempt at a solution

    Here is what I tried. I calculated Req for the entire system by V/I = 2.039. Since there is already a 2 ohm resistor in the first loop, the system can be reduced to one loop with the 2 ohm resistor and a 0.039 resistor in place on the 3 ohm. Now "X" is between this 0.039 resistor and the 2 resistor, so using Kirchoff's law I found that X has a voltage of 78.46 or 1.54. Does this seem logical? I have to admit I'm grasping for straws here.
    Last edited: Jan 15, 2010
  2. jcsd
  3. Jan 15, 2010 #2
    The "earth" symbol at bottom left means that point in the circuit is taken as zero volts for reference purposes.
    The voltage at X is simply, then, the pd between X and the earth point.
    One way you can find it is from the emf of the 80V battery and the pd across the 2 ohm resistor.
    Last edited: Jan 15, 2010
  4. Jan 15, 2010 #3
    Thanks, that sounds like a much simpler way of doing what I did!
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