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Sounds a daft question but I got thinking about another question and this cropped-up.

Background - In a conductor electrons move seemingly in a random fashion and more so when the conductor is warmer. When a voltage is applied there is a general tendency for electrons at one end of the conductor to start pushing electrons out at the other end i.e. there is a current flow.

But, as we are informed at school, the atom comprises mainly of empty space and, electrons appear to be a tiny object in that empty space so (with faint recollection of Heisenberg's uncertainty principle) and (ignoring anything I have previously learnt about how a BJT works), my question is this....

Question - If the plates of a capacitor were close enough would DC current flow?

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    \$\begingroup\$ I would think that if the plates were close enough that the distance between them was similar to the distance between the atoms among which electrons travel, then the plates are in fact touching. \$\endgroup\$ – Phil Frost Aug 11 '13 at 22:10
  • \$\begingroup\$ Not only does bring the plates close together cause QM tunnelling you may even be able to generate power through the use of Casimir effect. \$\endgroup\$ – placeholder Aug 12 '13 at 0:26
  • \$\begingroup\$ All conducting objects, indeed any object that can be charged, wires included, have a self-capacitance. Though I'm not sure if this is exactly what you're asking. \$\endgroup\$ – Bitrex Apr 30 '14 at 23:13
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I'm not a quantum mechanics expert, but short answer is YES! According to the quantum tunneling theorem found in here. Electrons can pass through dielectric and end up on the other side of the capacitor. In fact, there is a chance -however small- that an electron can exist somewhere in between the protons themselves.

http://en.wikipedia.org/wiki/Quantum_tunnelling

http://www.youtube.com/watch?v=EuU9Yin_2mM

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If the negative plate is hot enough, electrons are boiled off and moderate currents will flow with a fairly large gap and moderate voltage gradient. That's how vacuum tubes (valves) work.

If the voltage gradient is high and especially if it is pointy then field emission can cause current to flow. This has some special applications, but no practical components that I'm aware of.

If the insulating gap is extremely small (scores of atomic dimensions) and the voltage moderate, a current can flow via Fowler-Nordheim tunneling. This principle is used to program floating MOS gates.

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