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When the electrons flow in a circuit, so are those the electrons from the battery or are those the electrons of conductor like copper wire, etc..which are flowing in the circuit?

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Related question by OP: physics.stackexchange.com/q/53541/2451 –  Qmechanic Feb 11 '13 at 15:31
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2 Answers

You can never tell them apart, so I think this question makes no sense. All electrons are identical, there's no such thing as electrons from the battery or electrons in the wire..

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Both!

When you first connect the battery the electrons flowing are mainly the electrons that were in the conduction band of the copper wire before you connected the battery. However the electrons obviously have to flow through the battery to complete the circuit. If we take the example of an alkaline battery, electrons flowing into the battery anode react with MnO$_2$ to produce Mn$_2$O$_3$ and hydroxide anions. At the cathode Zinc reacts with the hydroxide ions to produce zinc oxide and electrons, and these electrons flow into the wire.

So while initially most of the electrons flowing are from the copper conduction band, the electrons flowing into the wire from the battery cathode have come from the chemical reaction in the battery. If you wait long enough all the electrons flowing will have come from the battery and all the electrons originally in the copper conduction band will have flowed into the battery anode and reacted there.

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This is a nice answer. I would only add that the initial movement of the electrons in the copper wire, is due to the electric field applied across the wire by the emf of the battery, assuming ideal battery. –  JKL Feb 11 '13 at 17:19
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