lightning

[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]

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?

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.

 

[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.

 

[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.

 

[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).

 

[positronicle]

This strike almost looks upside down.

https://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.

 

[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.

 

[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]

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.

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

 

[BeeBop]

One of the coolest pieces of art is made of lightning:

The Lightning Field, 1977, by the American sculptor Walter De Maria, is a work of Land Art situated in a remote area of the high desert of western New Mexico. It is comprised of 400 polished stainless steel poles installed in a grid array measuring one mile by one kilometer. The poles—two inches in diameter and averaging 20 feet and 7½ inches in height—are spaced 220 feet apart and have solid pointed tips that define a horizontal plane.

Walter De Maria: Lightning Field

 

[neon]

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

clouds because of friction of molecluoles biuld up a voltage charge and just sits there charged like a big capacitor waiting to find a path of less resistance to breakdown. the path can be any where another cloud earth any point that it can discharge the potential. when that happens because of the massive charge miles of cloud it discharges with millions of amperes for a very short duration. that generated heat sand can become glass or burn a hole in a tree. or if you lucky and wet it can pass on your dirty clothes and dissipate to ground.

 

[neon]

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.

absolutely wrong your skin has hi resistance. but dirt clothes has low resistance that is why they survive. and nobody yet has managed to measure the voltage or the current. hang in there

 

[Hero999]

That's true but where did I say otherwise?

Perhaps you've either misread my post or quoted the wrong post.

 

[Willbe]

sand that was turned into kinda glass

https://en.wikipedia.org/wiki/Fulgurite

 

[neon]

That's true but where did I say otherwise?

Perhaps you've either misread my post or quoted the wrong post.

you say above persons conduct better then trees.? i suggest that is because of dirt on clothes and evidence shows there is burnt clothes not holes in people heads. and trees for sure have more dirt on their bark then us on our skins. but there maybe some exceptions to the rule.

 

[Hero999]

I don't know about you but my skin is a better conductor than the cotton, nylon, acrylic, PVC clothes and I've never measure a tree but it's a safe bet to assume I'm more conductive than a tree.

Every piece of advice regarding lightning protection strongly recommends not standing under a tall tree.
http://www.weneedtostop.com/2008/07/10-struck-by-lightning-while-s.html
**broken link removed**
**broken link removed**

 

[Willbe]

you say above persons conduct better then trees.? i suggest that is because of dirt on clothes and evidence shows there is burnt clothes not holes in people heads. and trees for sure have more dirt on their bark then us on our skins. but there maybe some exceptions to the rule.

Some trivia:
The tree sap turns to steam instantly and causes the tree to explode when hit by lightning, so I guess the sap is the conductor.
I don't know the volume resistivity of tree sap.
The voltage, current and energy of lightning strike is readily available.

The IEEE standard equivalent circuit for a person is 1500 Ω in parallel with 0.1 µF, if memory serves me.
The skin is supposedly punctured by voltages >600v, and I have confirmed this.

 

[rjvh]

The skin is supposedly punctured by voltages >600v, and I have confirmed this.

It's a lesser nr of voltage

out of experiance I did catch a flash on my finger from a short out and it left me with a burst blister on my finger and that whas 380V

thanks for the earth leakage protection in place

Robert-jan