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I've always assumed that the strong resistance of air is the reason there is no flow of electrons between the terminals of a battery until a wire is connect. However, in a vacuum there is no resistive substance to impede the flow of electrons.

Does this mean that in a vacuum an average AA battery will spontaneously have a flow of electrons jump out of one terminal to the other?

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In a vacuum, the dc resistance to the flow of current is infinite. There is nothing contained within the vacuum that can conduct electricity.

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  • $\begingroup$ How would you determine the voltage necessary to cause a spark in a vacuum? $\endgroup$ – Vilhelm Gray Oct 11 '13 at 18:39
  • $\begingroup$ @VilhelmGray off the top of my head I don't know - if this is important I can do some research to re-acquaint myself. $\endgroup$ – Andy aka Oct 11 '13 at 18:43
  • $\begingroup$ @VilhelmGray I've decided against making my statement about the voltage being high enough to cause a breakdown. I now believe this to be incorrect in a perfect vacuum. $\endgroup$ – Andy aka Oct 11 '13 at 18:55
  • $\begingroup$ While I can imagine intuitively that there will be no current if an AA battery is in a vacuum, I don't think it's the empty space in and of itself that is preventing the flow of electrons (after all, atoms are mostly empty space). Rather, I suspect the distance between the two terminals may be the deciding factor. $\endgroup$ – Vilhelm Gray Oct 11 '13 at 19:10
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    $\begingroup$ @VilhelmGray I think the bigger problem is that at the surface of the battery you could probably not really describe it as a vacuum and tracking currents could form if the voltage was high enough. This happens on printed circuits between isolated tracks with fairly moderate voltages in the region of a few hundred volts. All that said I suspect the self-discharge of the battery may also be a factor vacuum or not. $\endgroup$ – Andy aka Oct 11 '13 at 19:27
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Vacuum tubes can conduct hundreds of amps of electricity quite readily. The effect depends on heating the negative terminal so that electrons can leave the metal surface which otherwise keeps them in the surface owing to a phenomenon called work function.

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