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Homework Help: Another resistence problem

  1. Mar 28, 2004 #1
    A question surprisingly similar to this:


    I = 1000amp
    V = 700,000volt
    distance = 100miles
    Resistence of the wire = .5 ohm / mile

    The resistence of my line is 50 ohms, original power is 7e5 * 1e3 = 7e8 watts. Final power, due to P = (I^2) * R, is 1e3^2 * 50 = 5e7 watts

    So finding the difference:

    7e8 - 5e7 = 6.5e8

    The answer given by the teacher is 50 MW (50e6 watts right?). A math error I'm sure, anyone see it?

  2. jcsd
  3. Mar 28, 2004 #2


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    Staff Emeritus
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    Gold Member

    I am not sure why you are computing the difference.

    The power lost by the line is


    End of story, you do not even need to know the total power transmitted.
  4. Mar 28, 2004 #3
    Maybe your teacher wants the power dissipated by the wire, and not the power that is left?

    Beat me to it. :smile:
  5. Mar 28, 2004 #4
    Yes sorry, read the problem wrong. Seems to be a common failing with this book, using obscure english to mask the real problem.


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