Is there a minimum electrical current that can be drawn?

Question

In simple terms, current flow is the movement of electrons along a conductor. Electrons are small, and even a small current involves millions of electrons.

Now consider inserting a resistance into a conductor. Fewer electrons flow. As the resistance increases, fewer electrons flow. Now picture a current flow equivalent to 1 electron per second.

Whatever that current may be (I'm curious as to what this value would be), if the resistance was increased further, would all current flow stop - as you cannot have a current flow of (say) half an electron. Or can you? Say one electron every 2 seconds? Is there a theoretical minimum, and if so, what is it?

Also, can it be shown in practice? If so, how?

Answer 1

1 electron per second works out to a current of 1.603E-19 amperes. When you're dealing with such extreme ranges the ordinary equations governing electrical circuits don't really apply, and you have to start treating the electron as a quantum entity. Even at much larger scales (semiconductors), you must treat the electron as a quantum entity to accurately predict its behavior. Ohm's Law doesn't apply as readily because quantities like 'resistance' are really simplifications of more complex phenomena. At some point before 1 electron per second, I suspect 'current' becomes a concept which is just not very useful. The SI definition, though, doesn't really establish a theoretical minimum.

It's also worth noting that the particle nature of electrons is apparent even at much higher currents. In signal detection there is a quantity called 'shot noise' which is basically signal noise due to the fact that electrons are particles and there is randomness in the times that they activate the detector.

Answer 2

The theoretical minimum for a current is ZERO considering that the wire is isolated (no forces that will cause the electrons to fly off from its atom) and the potential along the wire remains constant (voltage difference along the wire = 0). Remember that a voltage drop is what causes an electron to move from one point to another (we call that current), so if there is no or zero voltage drop an electron will remain in its position.

This will even make more sense if you recall Ohm's law: I=V/R ; I=current, V=voltage and R=resistance

No matter how high R is or if R reaches infinity if V is not zero, there will always be a small value for I.

Answer 3

You could say that there is a theoretical minimum. Once an object's resistence reaches a certain point, the object no longer efficiently conducts electricity (this point is undetermined, but I think I remember hearing it's somewhere around 1 nanoamp (one millionth of an amp)).

This is why any insulating material -- say wood -- doesn't efficiently conduct electricity (under certain curcumstances with large electric charges --such as with a lightning strike, even insulators can become conductive).

If you heat a conductor to a certain temperature, then it will eventually reach a point where its resistence is too high and no current will flow.

So, yes, there is a theoretical limit. I can't find any sources for you of this in practice.

Answer 4

One electron per second would be a current of 1.6 * 10^-19 Amps. This is a billion-billion times less than your house uses.

I can't think of why there would be a lower limit on current, unless there's some quantum effect that comes into play. The electrons do not have to actually "strike" some part of the circuit in order to transmit energy (the electric field that surrounds them can be "felt" in other parts of the circuit, so they can "push" on things from relatively far away).

But just how you would manage to generate such a current--and what it could be used for--I can't imagine.

Answer 5

since

1 amp = coulomb/ second = 6.25 E 18 electrons/second

1 electrron/ second = 1/(6.25e18) amps
or 1.6e-19 amps
or 1.6e-7 pico amps

This would be considered an insulator not a conductor and the movement of a single charge like that would be considered an electrostatic effect not a current. This is the sort of thing that happens when one rubs fur on rubber and so on.

Answer 6

I have had a few a beers, but this is a good question. Of course the temp needs to be figured in. I will save this for tomorrow and hit it with a fresh head!!!