On Friday, August 25, 2023 at 12:24:03 PM UTC-4, Commander Kinsey wrote:
How can lightning build up a charge when it's damp? Static electricity doesn't work that way if you rub a balloon in humid weather.
It's a dynamic process, based on the differential fall rates of droplets depending on their sizes.
Imagine droplets in an updraft, strong enough that the small drops are lifted while the larger ones are
falling. Due to the Earth's electric field, these drops are polarized, with positive charges on
their lower halves and negative above.
When there is a grazing collision between a small droplet and a large, the negative area of the small droplet will
come into contact with the positive area of the large. Charge will be exchanged, and when the two droplets
separate, the small will be positively charged and the large negatively charged. If this process carries on long
enough the upper reaches of the cloud will amass a large positive charge, the lower a negative. If this grows
large enough, the conductivity of the air will allow lightning, from the negatively charged region to the
positive, from the negative to the ground, or to another cloud.
Of course, things are really more complex than the simple scheme given above. Ice is always, or nearly
always, present along with liquid water. Charge separation works more efficiently with ice particles
added to the water.
Bernard Vonnegut and others ran experiments with a strong electric field at ground level which
produced clouds with a reversed charge distribution.
William Hyde
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