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Transmission lines 2 wires ?

  1. Mar 6, 2012 #1
    Hello, a beginners question here.
    Can someone please tell me why transmission lines use two wires instead of just one ?
     
  2. jcsd
  3. Mar 6, 2012 #2

    Drakkith

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    Staff: Mentor

    It takes two lines to complete the circuit. With only one line the current wouldn't be able to get back to the source, which is required in a circuit.
    Think of a loop of pipe that contains water. If you put a pump in there the water goes round and round. If you do the same in a straight pipe that's capped off, the water has nowhere to go, and doesn't flow. A similar effect happens with electricity.
     
  4. Mar 7, 2012 #3

    davenn

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    Science Advisor
    Gold Member

    Yes and no.....

    dont forget that there are were many transmission lines both power and communications
    that used just 1 wire and an earth return

    Dave
     
  5. Mar 7, 2012 #4
    If you do the same in a straight pipe that's capped off, the water has nowhere to go, and doesn't flow. A similar effect happens with electricity.
     
  6. Mar 7, 2012 #5

    Drakkith

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    Staff: Mentor

    True. Per wiki on Single-Wire Earth Return:

    So I would say that the 2nd wire completes the circuit because it is more efficient than using the Earth as the return.
     
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