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As we know lightning is basically electrons jumping from the clouds to the positives on the ground (trees, buildings...) in order to form a strong atomic bond. Well, why aren't they feeling a force that pushes them towards the target (Earth), like magnets? We know about the classical balloon electrostatic demonstration, and there the balloon is attracted or repelled from your hair or the wall, we don't see electrons jumping up (sparks)?

Also when we are charged and we get very close to a door knob, a little spark also forms. These must be the electrons jumping from my finger to the door knob, but why? Shouldn't my hand get attracted to the door knob?

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  • $\begingroup$ there is no jumping as you seem to think. have you read up the wiki article?en.wikipedia.org/wiki/Lightning#Electrification $\endgroup$ – anna v Mar 11 '18 at 17:13
  • $\begingroup$ If there is no jumping, then why is there a spark (lightning)? $\endgroup$ – Novalium Company Mar 11 '18 at 17:15
  • $\begingroup$ It is a current due to the large potential difference , there are consecutive bumps, see this practicalphysics.org/sparks-air.html $\endgroup$ – anna v Mar 11 '18 at 17:31
  • $\begingroup$ I got it, but there is no voltage or current going through the clouds or the ground? Why does a spark form? $\endgroup$ – Novalium Company Mar 11 '18 at 17:44
  • $\begingroup$ There is a potential difference generated by the separation of charges due to the upwinds and down winds in stormy weather as seen in the fist link during storms $\endgroup$ – anna v Mar 11 '18 at 19:14
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As the tag of your question shows, your question is about electrostatics.

Lightning strikes can occur from cloud to cloud, and from cloud to ground. As you point out, when objects are electrostatically charged (with opposite charges) they are attracted to each other. Best known example: rub a full head of hear with a balloon, and the balloon and the hair will be attracted to each other. (And they are both such poor electric conductors that they tend to remain statically charged for quite a while.)

So I think your question is a good one. If a cloud becomes electrostatically charged, then why isn't it pulled all the way down to the ground?

Let me first discuss the everyday experience that you mention, the little spark that may jump when your hand is not at the same electrostatic potential as the thing you are touching. There is actually only a very small electrostatic charge involved there. The little spark startles so much because your fingers are very sensitive to it. The cells of the nervous system use the tiniest of flow of ions across membranes to transmit signals from cell to cell. Very very little is enough to trigger that signal pathway. In the case of the little spark the actual electrostatic charge is very small, I'm sure the corresponding electrostatic attraction force is way too small to be noticable.

Now clouds.

Let me present an educated guess here.

Clouds are buoyant. I think it's actually quite hard to make a cloud descend. Let's assume that when electrostatic charge builds up between a cloud and the ground there is a significant electrostatic force. Let's assume that makes that cloud descend somewhat. As that cloud descends it enters more dense air, so it experiences more buoyancy force. That makes it hard for that cloud to descend further.

Conversely, when a cloud finally loses a lot of charge by landing a lightning strike, will that make that cloud immediately ascend, as it suddenly experiences less electrostatic force. Again, I don't expect it to ascend much, because the air above it is less dense, so that cloud will have less buoyancy there.

So:
I think it's plausible that the clouds have sufficent buoyancy to prevent being pulled all the way to the ground.

It could be that transient electrostatic forces play a significant role in atmospheric movements (during storms), but it could also be that any effects of the electrostatic forces are completely swamped by much larger general violent motions that occur during storms.

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