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How a Good Conductor is always a good Conductor

  1. Oct 4, 2008 #1

    I have a doubt in my mind about the behaviour of Good Conductors. So far whatever we studied,
    1. Good Conductors have free electrons to move and carry the charge,
    2. Electric charge is being carried in form of electrons.

    Now the question is Suppose, we have piece of good conductor(copper).

    B(+) =====COPPER_WIRE======== (-)A

    Scenario 1
    In above arrangement, in the copper is connected to (-)ive charged source (point A),
    and point B is open in the air..

    : How come the (-)charge will flow from Point A to the loose end point B.
    When we say Point A is Negative source, Is it like a electron gun, bombarding free electrons and pushing electrons into the metal wire ?

    : If there is no electron gun of free electrons and its only the charge(more exicted state of electron) which is getting transferred from electron to electron, then charge should also flow thru bad conductors also. Atleast the charge(excited state) of electron can be transferred from rigid packed electron of the atom of any bad conductor.

    : Now charge cannot flow thru bad electrons as we all know, and hence we need free electrons to take the charge and move further to +ive side or somewhere.. but in a finite direction..

    : But isnt a situation will come, where are the free electrons are clubbed at the B side of wire, and there will not be any free electron on A side, As all the electron are already moved and carried the charge. Then how come wire will still be Good Conductor.

    Please anyone try to explain the core, I know I am loosing some basics here

    Thanks in advance
  2. jcsd
  3. Oct 5, 2008 #2


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    Science Advisor

    No, it is not like an electron gun, it is just like an electron pusher. The electrons in a good conductor are free electrons, so they will get pushed together. But electrons don't like to get bunched up, because like charges repel, so the electrons will start pushing back once they get bunched up. Finally they will stop moving when the are pushing back as hard as they are being pushed.

    In a closed circuit, they don't stop moving, because they are connected in a loop, and the will go round and round forever. Thinking of it this way, the situation you set up is an open circuit through which current doesn't flow continuously. When you switch on the lights in a room, you are converting an open circuit to a closed circuit.
  4. Oct 12, 2008 #3
    Thanks for the reply atty,

    What is this electron pusher. Is it the electric flux ? If we see from the very begining ... the electric generator who is generating the current. pls refer the first picture here http://www.physclips.unsw.edu.au/jw/electricmotors.html

    Now in the arrangement between the N/S pole magnets, we are rotating the piece of wire. Due to the magnetic force.. electrons will drift and hence move further in one direction... Is this the push you are talking about?

    Now lets say electrons are moving continously and pushing other electrons which makes flow of electrons and hence electric current

    But after certain time all the free electrons will go from the rotating wire(the coil inside the generator) and there wud not be any free electrons to push further... unless the other end of wire (which is goin out of generator station is looping back to get the free electons which were pushed back earlier)

    Am i on right track on this ?

  5. Oct 12, 2008 #4
    Voltage, potential difference, is the pusher. Think of voltage as the PRESSURE in a water system, think of the movement of the electrons in a conductor as the water flow. Electrons move because they are charged....regardless of the source of voltage, whether emf induced via a field in a rotating device or via chemical means in a battery, electric potential can push electrons along especially when they are abundant and weakly bound to the nucleus.
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