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Homework Help: How can you get power used from step down transformers

  1. Apr 13, 2005 #1
    Suppose there are two transformers between your house and the high-voltage transmission line that distributes the power. In addition, assume that your house is the only one using electric power. At a substation the primary of a step-down transformer (turns ratio=1:29) receives the voltage from the high-voltage transmission line. Because of your usage, a current of 48 mA exists in the primary of this transformer. The secondary is connected to the primary of another step-down transformer (turns ratio=1:32) somewhere near your house, perhaps up on a telephone pole. The secondary of this transformer delivers a 240-V emf to your house. How much power is your house using? Remember that the current and voltage given in this problem are rms values.

    Im lost :confused:
  2. jcsd
  3. Apr 13, 2005 #2


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    Hint: The voltage steps up as you move back towards the High voltage line, and power in equals power out.
  4. Apr 14, 2005 #3
    I dont know if this is right...
    but heres what i did
    Is = IpNp/Ns
    =48*10^-3 * 29 = 1.392A
    Is = IpNp/Ns
    =1.392A* 32 = 44.544A
    P(avg) = Irms*Vrms = 44.544A * 240V = 1.1*10^4W

    is this right?
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