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Homework Help: Need help on transformers

  1. Mar 9, 2005 #1
    A transmission line that has a resistance per unit length of 4.5*10^-4 ohms/m is to be used to transmit 5 MW over 400 miles (6.44*10^5 m). The output voltage of the generator is 4.5 kV.
    a) What is the line loss if a transformer is used to step up the voltage to 500 kV?
    b) What fraction of the input power is lost to the line under thses circumstances?

    For part A, I used P1=I1^2*R and solved it for I1. Then I used I1*V1 = I2*V2 and solved it for I2. Next, I got the power using I2 and subtracted P1 with the power that I just got. The answer is wrong though...
    Can anyone help plz? Thx!! :)
     
  2. jcsd
  3. Mar 9, 2005 #2

    dextercioby

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    Homework Helper

    I don't know how u define the "line loss",but you can easily compute the lost power due to Joule effect.

    What is the current running through the wire in both cases...?Give the method & result.

    Daniel.
     
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