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Alternating current.

  1. Nov 2, 2009 #1


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    Can someone please explain how the current regularly changes direction after some time in alternating current? I mean if it changes direction, how does it move forward?
  2. jcsd
  3. Nov 2, 2009 #2
    Hi there,

    You have to understand that it is not necessarily a current like water flowing through a hose. In an electrical wire, the electrons are submitted to an electric field. In a DC current, the electric field is continous, and pushes the electron forward. But the electrons make direct hit with the atoms in the wire, therefore being constantly slowed down, to a few cm per hour.

    In an AC current, the electric field changes direction constantly. The electrons present in your wire will therefore go back and forth, creating the current and the potential work done on the appliance. Therefore, you don't need it to move forward, since electrons are everywhere in the wire.

    Hope this helps. Cheers
  4. Nov 3, 2009 #3


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    Can you explain it a little simpler? Which electric field are you talking about, that is continous and pushes electrons forward in DC?
  5. Nov 3, 2009 #4
    Hi there,

    I'll try to give you simpler explanation.

    To generate a current AC or DC, you need voltage. I'll keep with the copper wire example. A certain voltage is applied at both ends of your circuit. Voltage is just another way of saying that an electric field is created in the wire.

    Remember that electrons, being electrically charged particles, will only react under the influence of an electric field.

    Ok, so you have an electric field that forces your electrons to move. Fact is that the electrons in your wire are not coming from very far. They are taken right there on the spot, using the "free" electrons of copper atoms.

    Now to make my story complete, it is the movement of electrons that will make the work in your device (mp3 player and so on). Therefore, whether the electrons are always pushed in the same direction, or whether they change direction, as long as they move.

    Is this any clearer now???

  6. Nov 3, 2009 #5


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    Yeah. That made it alot clearer. Thanks
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