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If electricity is a flow of electrons in a wire then eventually all electrons will leave the beginning of the wire and reach the end of the wire. Is that possible? Why if not? What will happen then if yes?

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    \$\begingroup\$ But more electrons are added back to the beginning of the wire by virtue of a closed circuit (oversimplification, but...) \$\endgroup\$ – Tom Carpenter Nov 15 '16 at 21:04
  • \$\begingroup\$ Electrons are also constantly generated (and recombining) due to thermal generation and carrier injection. \$\endgroup\$ – jbord39 Nov 15 '16 at 21:55
  • \$\begingroup\$ Beware of the "empty-pipes fallacy." Wires are not like empty pipes with electrons injected into one end. Wires are like pre-filled pipes, always containing tens of thousands of coulombs of mobile electrons. \$\endgroup\$ – wbeaty Nov 16 '16 at 6:41
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A battery is a device which has a bunch of electrons on one side of it and a lack of electrons on the other side. When you put a wire between the contacts, the electrons run to the other side until there is charge balance. Then, you're right, no more electrons will flow. You have to recharge the battery or get a new one. Note that even when you "run out" of electrons in the charge balanced case, all of the electrons are still there, they're just in a different position. Some are left in the wire; most are back in the battery just in equal amounts on each side of the battery.

In short, you're right though.

With AC power, you're pushing and pulling electrons 60 times a second in order to extract work out of them. In that case, all of the electrons are always there and don't really move unidirectionally unlike the battery case.

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Electrons will flow through the wire towards a higher potential. However, they do not all leave one side and travel to the other.

If 1A of current is travelling through a wire, then 1 coulomb or approximately \$6.241\cdot10^{18}\$ electrons are passing a given point in the wire per second. If you have a power source such as a battery, eventually an equilibrium is reached as the battery discharges, and there is 0V of potential difference across the wire. At this point there are still electrons on both sides of the wire, but since there is no potential difference, there will be no current flow, so the electrons stay there.

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  • \$\begingroup\$ "and there is 0V of potential difference across the wire" - not if the wire has any resistance (hint: it does) and a current is flowing through it. \$\endgroup\$ – Tom Carpenter Nov 15 '16 at 21:17
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    \$\begingroup\$ The wire does have a non-zero amount of resistance, but unless you have an infinite power supply behind this circuit, eventually it will deplete and current will drop to 0 (and therefore voltage). If you assume there's always current (which indeed makes my statement invalid) then this question doesn't really make sense, since there will always be more electrons to travel across the wire. \$\endgroup\$ – Nathan Nov 15 '16 at 21:29

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