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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?

    (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


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