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Noob Question.

  1. Mar 7, 2010 #1
    Hello all, This is my first post here, and I've got something that is stumping me. no this is not for homework, My question is this, When electricity is generated, where do the electrons come from? I mean if they we're coming from the copper wires, or magnets inside the dynamo wouldnt we see some sort of erosion, an isotope change, and radioactivity?

  2. jcsd
  3. Mar 7, 2010 #2


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    Staff: Mentor

    Welcome to the PF.

    The electrons are being pushed from atom to atom in the conductive circuit (like around a wire) by the "electromotive force". There is not an excess of electrons, they are just being pushed along by some power source like a battery or power supply.

    The only time you get an excess of electrons (more electrons than atoms) is when you collect them as part of an electrostatic charge (like the ESD shocks you get from rubbing things together).
  4. Mar 7, 2010 #3
    Thank you for the response! I really appreciate it. However I'm curious, since there being pushed along, that means some atoms somewhere are having to lose an electron. which would denote some sort of erosion, an isotope change, and radioactivity?

  5. Mar 7, 2010 #4


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    Staff: Mentor

    In conductors like metals, there is a band of electrons that is "shared" between the atoms. So the electrons in this conduction band are moving from atom to atom randomly anyway. when you apply a field down the wire with a battery or whatever, they still move mostly randomly, but tend to drift in the direction of the postive terminal of the battery or power supply.

    You can look up the Band Theory of Solids for more info. Here is a brief wikipedia page on Conduction Band, with links to more info.
  6. Mar 7, 2010 #5
    Just for your information, Jason

    Since you have heard of electrons I assume you have some idea of the the make up of atoms?

    Erosion refers to whole atoms (usually lots of them)

    Loss of electrons makes ions not isotopes.
    Isotopes are determined by the neutrons in the atomic nucleus.
    Loss of (or gain) of neutrons would definitely make new isotopes
    Loss/gain of protons makes new elements

    finally most radioactivity comes from the nucleus. not form the action of electrons (luckily for mankind) so we can safely use elctic gadgets without generation of radioactivity.
  7. Mar 7, 2010 #6
    Thank you again that's what I was looking for. I appreciate your patience :biggrin:
  8. Mar 8, 2010 #7


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    You have been told that you need a complete circuit for a current to flow. This is because you very soon run out of electrons to move along a piece of wire if there aren't fresh ones to enter and make up for the ones that have left. Actually adding or taking away electrons involves 'charging up' an object and this requires enormous voltages for even a small charge imbalance - much more than your average battery supplies.
    If you have ever seen a Van der Graaff generator working you will have seen huge sparks but the actual amount of charge stored (and hence the average current flow as it discharges through your finger etc.) is very small.
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