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Homework Help: Transmitted power

  1. Sep 20, 2008 #1
    1. The problem statement, all variables and given/known data
    A high-voltage transmission line with a resistance of 0.28 /km carries a current of 990 A. The line is at a potential of 740 kV at the power station and carries the current to a city located 162 km from the station.
    (a) What is the power loss due to resistance in the line?
    W

    (b) What fraction of the transmitted power does this loss represent?
    %



    2. Relevant equations

    Power= change in V^2/R

    where v is potential difference and R is resistance

    Power = I^2*R

    where I is current



    3. The attempt at a solution

    I got part a correct. I used the equation p=I^2*R and got 44457336
    I cant figure out how to get the second part though
    I tried using p=v^2/R with 740,000 as the V and .28(162) as the R to no avail

    any suggestions?
     
  2. jcsd
  3. Sep 20, 2008 #2
    If you notice, V/R does not give a current of 990 A. The concept gets a little more complicated with a transformer. I*V (990A*740kV) is the provided power. I^2*R is the power lost to resistance.
     
  4. Sep 20, 2008 #3

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Hi goWlfpack! :smile:
    p = IV? :wink:
     
  5. Sep 20, 2008 #4
    got it! thanks guys! :)
     
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