# B Limit to generating static electricity via contact?

#### atommo

Summary
Can you run out of electrons when continuously rubbing two materials together (and discharging one) to create static charge?
Let's say you are rubbing a balloon on your hair to make it charged. If you then discharge the balloon and rub it on your hair again (and repeat this process numerous times). Would your hair run out of electrons so eventually you would be unable to charge the balloon, or would your hair gain electrons from elsewhere before this point?

I was reading up on how thunderstorms make lightning and that the particles collide/separate out with different charges (top of the cloud becomes positive, bottom of cloud is negative). In this way, if all the lightning of a thunder cloud strikes the ground (and not the top of the cloud where all the positive particles are) [this is purely theoretical as it is highly unlikely that would actually happen] then the top remains positively charged. Would this in theory mean a thunder cloud could 'run out' of lightning (as the bottom particles couldn't gain more electrons)?

Sidenote: My understanding of thunderstorms is that ice particles become negatively charge while water particles become positively charged. They collide with each other because of the extreme winds in a storm cloud. The lighter water particles get blown upward by updrafts while the ice is heavier so stays lower down. This is how the negative/positive separation occurs. (Reference: How does lightning form?)

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#### davenn

Gold Member
Summary: Can you run out of electrons when continuously rubbing two materials together (and discharging one) to create static charge?

I was reading up on how thunderstorms make lightning and that the particles collide/separate out with different charges (top of the cloud becomes positive, bottom of cloud is negative). In this way, if all the lightning of a thunder cloud strikes the ground (and not the top of the cloud where all the positive particles are) [this is purely theoretical as it is highly unlikely that would actually happen] then the top remains positively charged. Would this in theory mean a thunder cloud could 'run out' of lightning (as the bottom particles couldn't gain more electrons)?
There is an almost continuous incoming of charge into the Earth's atmosphere, mainly from outer space

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#### atommo

Interesting. So thunderstorms can't really run out due to outer space radiation.

However, what about the example of a balloon and hair/fabric? Since that would be on the surface, I'm guessing there aren't so many free electrons available to 'recharge' the material losing electrons.

#### atommo

Since I haven't heard anything else I asked around elsewhere:

Q: if particles (lets say dust particles) became positively charged and their only contacts were the material stripping their electrons and filtered air, would they completely lose their electrons and not be able to charge the material they're contacting (such as silicon) after a certain amount of time?

A: yes, or at least, they have reached charge equilibrium with their environment, and will not be able to supply electrons until it acquires them from some other source in the environment that is out of equilibrium.

Which is what I expected.

I was curious about this since devices like the Wimhurst Machine don't actually lose electrons to the earth- they flow around in a circuit (so while material does lose electrons, it gains those same electrons back later after the static discharge)

"Limit to generating static electricity via contact?"

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