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Might be more of a physics question, but what happens when you connect a wire only to the negative (or positive) terminal of a battery, in terms of electron movement? Do electrons flow in/out of the wire until equilibrium is reached?

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  • \$\begingroup\$ No circuit, no current flow. Practically, electrons will continue a net-zero-current drift and move between places in the metal due to thermal energy. \$\endgroup\$ – user2943160 Jul 8 '16 at 23:55
  • \$\begingroup\$ Perhaps a handful of electrons will flow, but not nearly enough to do anything useful. For all practical purposes we say no electrons flow. \$\endgroup\$ – user253751 Sep 11 '16 at 11:52
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In short, absolutely nothing (*).

If you only connect one end, there is no complete circuit and as a result no current can flow.


(*) There may be a small current flow for a very short period, but in all likelihood it will be such a short period and such a small amount of charge that you wouldn't be able the measure it.

The reason for saying this is there will be a very very very tiny capacitance (probably so small it cannot be measured) between the other end of the wire and the other terminal of the battery. This will form a complete circuit which will allow a small amount of current to flow during the transient voltage period when the wire is connected.

But again, it is such a small immeasurable amount that you can effectively consider it irrelevant - cosmic rays would probably cause more current to flow in the wire!

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    \$\begingroup\$ Thanks, makes sense -- I was thinking about an antenna, how it only connects at one end, but there is still some current moving in and out of it? Sorry for the newb questions :) \$\endgroup\$ – user1630799 Jul 8 '16 at 23:30
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    \$\begingroup\$ @user1630799 things get less simple when you start considering RF frequencies. But in essence antennas typically have some form of a ground plane and there is capacitance/inductance between the antenna and the ground plane. \$\endgroup\$ – Tom Carpenter Jul 8 '16 at 23:32

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