Phase, neutral & Earth Again

Discussion in 'General Electronics Chat' started by aamirali, Mar 26, 2012.

  1. aamirali

    Thread Starter Member

    Feb 2, 2012
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    1. I have attached two ckts. One showing ac sourrce powering a bulb. It also shows its curent direction during +ve & -ve half cycles, (Figure 1)

    2. What we do in villages, is powering tubewells with two wires-> phase wire & second is digging the earth & then creatng earth there. Now tubewells have only two wires - phase & earth. It works.

    I don't understand how to explain current flow direction as in 2 pdf.

    Current can't flow out of earth. Otherwise this way energy can be drawn out of earth :) & it solves our energy needs.
     
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    • 2.pdf
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  2. studiot

    AAC Fanatic!

    Nov 9, 2007
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    It would help if you rewrote your question in English.
     
  3. wmodavis

    Well-Known Member

    Oct 23, 2010
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    Current flows in a circuit depending on the polarity of the forcing voltage.

    You are simply wrong in saying "Current can't flow out of earth" Where could you have possibly gotten that idea?
     
  4. strantor

    AAC Fanatic!

    Oct 3, 2010
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    in your second PDF, you show using the earth as a conductor. This CAN work. Actually, the earth is a very good conductor, and current CAN flow through it. In your drawing, the current is not being magically produced by the earth, it is being produced by your sine source, simply using the earth as a conductor - think of the earth as a wire..

    This method is not safe; usually the earth is reserved for safety ground and not an active circuit component.
     
  5. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Careful, what is the resistivity of the granite underlying New York?

    It is better to regard the Earth as a (nearly) infinite source or sink in circuit terms.

    "An earth is a circuit element that does not change in potential, regardless of the current into or out of it, within the limits of consideration. "
     
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  6. aamirali

    Thread Starter Member

    Feb 2, 2012
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    1. Hi as I posted circuit in 1.pdf, current flow in ac can understood. During +ve half, current flows in one direction & during -ve half current flows in opposite direction.
    Right am I right till now. This is how ac signal works.

    2. Now in case of second end is earthened (besides its dangerous, but it is done & it workss also, don't know how). During +ve hale cycle, lets say current start flowing in one directiobn & goes to earth to complete the ckt.
    But how to explain this path in case of -ve half of cycle.
    Plz tell me the current path in case of +ve & -ve half cycles
     
  7. wmodavis

    Well-Known Member

    Oct 23, 2010
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    Earth CAN be a good conductor depending on what it is composed of and whether or not it is damp or wet.

    aamirali
    1. you are correct in #1
    2. 2.pdf wired using the earth as a conductor is not necessarily dangerous but it can be. It does work as you have observed. It works just like the circuit in diagram #1. The only difference is that the conductance of the earth now replaces one part of your circuit. In this case think of the earth as a wire completing the circuit. It is really not very complicated. The earth conducts electrical current just like a wire does though its resistance is more variable, less certain and likely higher than the wire.
     
  8. aamirali

    Thread Starter Member

    Feb 2, 2012
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    Then how to define current path.
    Like in 1.pdf, current flow can be mentioned & decsibed.
    Similarly, in case of 2. pdf, how to show current path. One side, Phase line has return path neutral. But on other side it is connected to earth. For a moment, let say during +ve half cycle current flow in one direction. Then during -ve half cycle how to define current path.
     
  9. evilclem

    Member

    Dec 20, 2011
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    The current path is the same for both cycles, just in the opposite direction. As everyone has already said, the Earth acts as the return wire (acts as the neutral).

    Single Wire Earth Return (SWER) is quite common in remote locations.
     
  10. aamirali

    Thread Starter Member

    Feb 2, 2012
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    Hi,
    So during -ve half cycle, first current flows in direction -> into earth from source side, then it comes out from earth from load side.
    How could this happen
    Earth is sink. its nor source I think
     
  11. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Did you read my post#5?


     
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