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Representation of a 1 phase transmission line as line charges

  1. Jul 26, 2013 #1
    Hi,
    According to what I understood, when a terminal is connected to a line, it causes electrons to flow in one direction. And so for a single phase transmission line in parallel if connected to supply, then in one side electrons will be flowing in one direction and the same electrons will be flowing in the opposite direction in the other transmission line.
    In normal representation in books, this transmission line is represented as 1 line carrying positive charges(Q) which are linearly distributed in the line and the 2nd line carrying charges with opposite polarity(-Q). How it can be represented like this, I cant understand the concept when I think in the way of electrons movement? Please help me on this, i need somebody. Any replies will be appreciated....
     
  2. jcsd
  3. Jul 26, 2013 #2

    marcusl

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    The electrons are different, but the total current in each wire is the same.
    Are you perhaps confusing current with charge? The current changes sign in the two wires because the direction of flow is opposite.
     
  4. Jul 28, 2013 #3
    Sir,
    First of all, i am thanking you for showing interest in my post. Actually no sir, i am not confused i think. Actually a current in one direction means charges are flowing in one direction and so for an AC transmission line charges will be moving in both direction alternatively.
    But consider the positive half of the AC wave at the sending end. Looking from top of the line, in the sending end, line's charges will be moving in one direction and in the receiving end line, charge will be moving in opposite direction. And in text books, this condition of transmission line is depicted as a pair of lines one carrying +ive charge and the next carrying -ive charge and i am confused with this depiction. How can a charge flowing in one direction(i.e. current in one direction) be said in terms of signs, i.e. -ive or +ive??
     
  5. Jul 29, 2013 #4

    marcusl

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    Your terminology is fine until you say "this condition of transmission line is depicted as a pair of lines one carrying +ive charge and the next carrying -ive charge." These are not charges but currents; note that i and I are the traditional symbols for current. In this case, the sign simply denotes whether current is flowing away (+) or towards (-) the ports.
     
  6. Aug 1, 2013 #5

    sophiecentaur

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    I have never seen this in any text book. Wires do not carry "positive" charges. The current carriers are always negative electrons in metals. The sign refers to current in any diagram you will have seen.
    A positive charge flowing in one direction is certainly the equivalent Current to a negative charge flowing in the opposite direction but that is not relevant here.
     
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