Electrical energy

[Primarygun]

When a beam of lightning hits a tall tree, the tree catches fire and broken down because the energy gained causes the water inside becomes steam.

What happens when a beam of lightning hits a black carbon solid?

[nomadd22]

It doesn't have to be water. Andthing that conducts enough electricity in a short enough will heat up and explode.

[5614]

Although, if that is right, it depends on the compound/element because air doesnt explode when lightning occurs.

[YT2095]

the carbon vaporises along the shortest electrical (most conductive) path turning it into CO2 and leaving a "trail" of hollowness or a "Trench" along the pathway, it may be considered as next to and almost as good as a Metal for conduction, infact it`ll take a Carbon path sooner than a Rain water one

[mmalluck]

Although, if that is right, it depends on the compound/element because air doesnt explode when lightning occurs.

 

Ever hear thunder? That's the sound of the air violently expanding outwards due to the intense heat of the lightining bolt. The air explodes.

 

As YT said, lightning will take the path of least resistance, but even a little resistance can cause the substance to vaporize when a lightning bolt hits it.

 

To give you an idea:

Strong lightning strikes can produce currents in excess of 200,000 Amps.

 

Lets say the bolt chooses to go through some heavy copper wire on it's way to ground. We'll say it's 10 meters of 0 AWG wire.

 

Using a handy-dandy wire gauge resistance chart we can see this wire has a resistance of 0.0032242 Ohms. That's a pretty small resistance.

 

How much power will this resistor (the wire) have to dissapate when the lightining bolt pass through it?

 

P=(I^2 * R)

 

P=((200000 amps)^2 * 0.0032242 Ohms) = 128,968 Kilowatts

 

The wire quickly becomes plasma.

[srh]

I think I read somewhere that lightning heats the air in close proximity to around 6 times the heat of the suns surface...what's that, about 20 000 degress C!

Which begs the question: how do people survive lightning strikes with only burns and missing eyebrows, considering that immense heat?

[mmalluck]

1) they didn't actually get struck by the bolt, they were just close enough to get blasted by the hot compression wave the bolt produces.

 

2) The duration of the bolt is so short, that the heat capacity of the body prevents them from becoming burning up.

 

In all fairness my wire example didn't take the duration of the bolt into account. If the bolt was very short, the copper wire could survive. Peak power disapation may be 128,968 Kiliowatts, but if the bolt only last microseconds, considerably less heat will be transfered to the wire.

[srh]

Thanks.

I knew I was missing out on some critical points.

 

Do you have any idea of the vicinity within which a human could be of a strike, and still have a chance of survival?

[mmalluck]

That's a hard one to guess.

 

I depends on the size of the bolt, the kind of bolt (positive or negative) and the enviroment.

 

If the soil is a poor conductor, the bolt will spread through the ground and can electrify a much larger area, as compared a bolt produced over soil that conducts better.

 

For instance here's a picture of the scortch marks left from a lightning strike on a flag pole that was left in a field.

 

 

The scortch marks are about 25 feet across. If you were standing anywhere around there, you wouldn't be feeling too happy.

 

Just because this thread made me think about this pic, I'll put it up as well. The person who took this picture survived. Click the picture for the orginal source page. They have some other very impressive electrical accidents (exploding utilities and the like).

 

And here's the story that goes with it:

The above photo is courtesy of Kane Quinnell - and it was almost his last. The above lightning stroke was almost certainly a "Bolt from the blue" - a relatively rare positive lightning bolt that originates from the top of a distant storm cloud rather than from the negatively charged cloud base. These massive bolts can travel horizontally for 10 miles or more from the center of the main storm. They can pack peak currents of up to 340,000 amperes, and they last for tens or hundreds of milliseconds. This is about ten times more current and ten times longer than regular (negative) lightning. These bolts are extremely hot, they do considerable damage to whatever the hit, and if you happen to be unlucky enough to get hit by one of these monsters, you DO NOT survive. Here's his description of what happened:

 

"I happened to be out in the back yard, watching a storm on Friday night (14/01/05) that appeared to be a few km away, (I live in Old Toongabbie, and the storm appeared to be in Pendle Hill, or Greystanes, Australia). I set the camera's settings so that the shutter remained open for four seconds, placed it on the back bumper of my car, hoping to get a few shots of lightning in the clouds a few km's away. There was no rain at all, and stars could be seen over the north 1/3 of the sky, so I did not feel in danger in any way. Boy was I mistaken... DO NOT UNDERESTIMATE ELECTRICAL STORMS - YOU COULD GET YOURSELF KILLED!

 

I clicked away a few times, and got nothing, and then clicked the button again, and within 0.5 seconds of me pressing the button, I had jumped at least 2 metres in the air, as I heard a tremendously loud crack of thunder, and see this amazingly bright beam of electricity right in front of me. I had then landed, grabbed the camera, and was inside the house within 2 seconds.

 

I did not realize just how lucky I was until I uploaded the pic to my computer, and saw a leader stroke that must have originated no more than 2 metres from where I was standing next to my car, under my carport. Had the main charge taken the leader near me, rather than the one it did, I would be dead.

 

When lightning strikes, it actually comes up from the ground first (called a leader stroke), this stroke makes the air within it conductive, and once it reaches the cloud, you have a complete circuit, and the bolt of lightning comes down from the cloud along the leader stroke. First leader to the cloud wins, luckily mine did not.

 

I estimate that the main bolt was approx 1.5- 2 metres in diameter, and struck something in the yard behind the shed that is located at the back of the yard. That would have had an extremely large charge, and would have been extremely hot, hotter than the surface of the sun, at 5,500 degrees Celsius, it could have been around 30,000 degrees Celsius. Needless to say, I was buzzing for the rest of Friday night, due to the amount of adrenaline going through me cause of how close it had come."

 

Kane Quinnell was one very lucky bloke!

[srh]

Wow, thanks.

Phenomenal pics. Strangely enough, that guy doesn't live far from where I live.

 

If the soil is a poor conductor' date=' the bolt will spread through the ground and can electrify a much larger area, as compared a bolt produced over soil that conducts better.

[/quote']

 

Wouldn't the bolt spread through the ground and electrify a much larger area if the soil was a better conductor, rather than a poor? Or do you mean in terms of the resulting damage, because of higher resistance?

[mmalluck]

Well I'm no expert on lightning, but I can speculate from what I know from electrical engineering and physics.

 

The goal of any lightning bolt is to get itself to ground taking the least resistive path possible. It wants a path that's short and conductive.

 

If the ground is a good conductor, the bolt gets itself to ground quickly and their's less chance of a bystander getting hurt. It's reminds me of the guys who work on live electric lines.

They literally clip on to the high voltage line while it's active. Thier body is raised to the potential of the line, but they're unaffected because the wire is a more attractive conductor than they are themselves, even if they touch the same wire in two different places.

 

Now soil is a funny thing, especially sand soil. The water in the soil will make it conductive, but as soon a lightning bolt strikes, all of the water becomes steam, and the soil dries. So the lightining bolt spreads to a more conductive part of the soil. Again the soil drys, so the bolt forks and moves again. That's how you get the spiderweb effect in the previous picture.

 

With poorly conductive soil, there's a lot more of the lightning bolt searching for the best conductive path for the moment. There's a better chance the bolt will choose part of you for that path.

[srh]

aahh, I see...I've always found it particularly difficult to understand electricity, or rather, electronics. I don't know why.

Very cool info.