rjvh

hi just wondering if sombody can explain this to me

so far i know the electrons flow from a negative pole to a positive one

but in the case of i lightning strike the positive ions build up in the sky and have a discharge to the negative pole (which is in most cases the ground)

is it than that the actual electron flow comes from the earth? according the the theory it should be

how can we explane the lightning flash that branched out in separate ways conecting it to the earth?

and how do we explane a lightning bold that first hit the surface and than travel to other directions until its power is absorbed by other points?

personaly i saw one in my life and the spot of impact was a small crater and sand that was turned into kinda glass but you still did see a track where it went then and that was still a 50 meters furter to an electrical distribution eclosure on the street



Robert-Jan

kchriste

Lightening bolts can come from positive (more rare) or negative (more common) charges in the sky. So most of the lightning travels from a negative charge in the sky to the positively (relatively) charged earth.

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dknguyen

I don't know whether positive or negative is more common in the sky- just that the earth is a giant source/sink for extra charge. But isn't there usually a smaller "leading" bolt that comes up from the ground to meet the larger main bolt coming down from the sky?

Perhaps the path is due to "the least resistance"? Except instead of wires it's air so you can see it. I suspect it is far more complicated than that though, and is in the realm fo electromagnetics. Lightning bolts like to hit where the electric field is most concentrated which tends to be at sharp points. From here it spreads out. It has to do with electromagnetics.

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3v0

The potential between the striking and the struck is reduced by a strike. If another target is close the lighting may move to the 2nd target after the first has had it potential reduced.

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Krumlink

Lightning branches out in several directions, because it is following levels of low resistance. When lightning travels through the air, it creates a large amount of Ozone, x-rays and gamma rays (reccently discovered).

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positronicle

This strike almost looks upside down.

http://youtube.com/watch?v=bNhY3Hx83fA&feature=related

MacFeegle

I've heard of lightning striking a tree, and then jumping to a nearby person, I guess only part of the current flow jumped since, in that case, the person survived.

ericgibbs

hi R-J,
Google for Red Sprites and Blue Jets you will find it interesting.

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Hero999

The lightning in the video is obviously positive because it flowed from the tower to the sky and not the other way round.

Lightning can jump from a tree to a person only if they're standing underneath the tree because people conduct electricity better than trees do.

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mdwebster

The potential is present in ionized gases. These ions are drawn to their opposite charge, the earth (or the cloud, depending on the polarity). The ionized gas, which has much lower resistance than non-ionized gas, forms streamers as it winds its way towards the earth. Once one of these streamers hits the ground (or a tree, or a lighning rod, or whatever), you have a fairly low-resistance path from one side to the other and BAM! Discharge.

There's an excellent article on lightning in the Feynman lecture series. I believe it's the second volume, near the front. All kinds of fun stuff like the average potential as you go up from the earth's surface is 100V/meter (i.e. the potential at 10 meters is 1000V vs. the ground). And how the average charge changes according to the time of day and is directly correlated with the number of thunderstorms occuring at any given time.

ericgibbs

hi,
IIRC, globally there are 11 lightning strikes per sec.
With a special receiver you can hear the strikes as a 'buzz'.

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BeeBop

One of the coolest pieces of art is made of lightning:
Walter De Maria: Lightning Field