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Homework Help: Another resistence problem

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

    https://www.physicsforums.com/showthread.php?t=17219

    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?

    Peter
     
  2. jcsd
  3. Mar 28, 2004 #2

    Integral

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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

    P=I2R

    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.

    Thanks.

    Peter
     
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