Author Topic: Lightening? (Read 9023 times)

Ding123 · « **on:** January 19, 2012, 08:50:09 PM »

Is lightening AC or DC?

I made a bet with somebody that I could find out beyond a shadow of a doubt.
If I can't , I will owe her a dollar.

JW · « **Reply #1 on:** January 19, 2012, 09:04:20 PM »

Its neither nor, Its plasma, the fourth state of matter.

Remember you can use a welder to strike an arc with either AC or DC. You use AC to weld aluminum (gtaw) and electrode positive for steels.

Norm · « **Reply #2 on:** January 19, 2012, 09:10:22 PM »

Most cloud to ground strikes ....negative strike from cloud but sometimes the cloud is positive to ground ....positive
strike but the single strike is well ... Direct(static ) Current......DC
but you can Google it just like I did.

Norm.

Norm · « **Reply #3 on:** January 19, 2012, 09:24:57 PM »

Quote from: Ding123 on January 19, 2012, 08:50:09 PM

Is lightening AC or DC? I made a bet with somebody that I could find out beyond a shadow of a doubt.
If I can't , I will owe her a dollar.

Well either way you will owe her a dollar....beyond the shadow of a doubt
you haven't learned not to bet with a woman....
Don't you know they always win ? LOL
Norm.

rossw · « **Reply #4 on:** January 19, 2012, 09:26:38 PM »

I don't wish to dispute what the demigod above has said, but I will share a little snippet of data - LIVE data - REAL TIME ACTUAL HARD FACTS data I have.

I run one of 7 national lightning sensors that continuously track lightning strikes over the whole of Australia and surrounding areas.
Here is part of the real-time data stream:

*AA FG 01/20/12 02:17:09.7020134 LAT=-12.92499 LON= 148.24890 AMP= 55.35K
*AA LG 01/20/12 02:17:40.2881254 LAT=-36.54343 LON= 149.09877 AMP= -23.73K
*AA DG 01/20/12 02:17:40.7988343 LAT=-05.72623 LON= 128.18067 AMP= -74.99K
*AA DG 01/20/12 02:18:31.6209960 LAT=-15.04343 LON= 136.18708 AMP= 76.65K
*AA FG 01/20/12 02:19:12.7330416 LAT=-10.55011 LON= 150.95625 AMP= 56.87K
*AA DG 01/20/12 02:19:28.9375167 LAT=-12.31532 LON= 147.38962 AMP= 51.11K
*AA FG 01/20/12 02:19:29.8993793 LAT=-08.66699 LON= 132.08056 AMP= -59.52K
*AA DG 01/20/12 02:19:38.4404562 LAT=-13.54535 LON= 136.48686 AMP= 48.15K
*AA FG 01/20/12 02:19:56.3250830 LAT=-16.13757 LON= 151.91399 AMP= 42.93K
*AA FG 01/20/12 02:19:58.9776589 LAT=-29.04079 LON= 147.24786 AMP= 62.26K
*AA FG 01/20/12 02:20:06.8492068 LAT=-17.33718 LON= 126.39274 AMP= -82.67K
*AA FG 01/20/12 02:20:14.4287370 LAT=-35.11160 LON= 147.14928 AMP= 11.52K
*AA LG 01/20/12 02:20:14.8085889 LAT=-35.91129 LON= 149.23288 AMP= -21.19K
*AA LG 01/20/12 02:20:14.8579376 LAT=-35.94441 LON= 149.25910 AMP= -8.58K

As you can see fropm the last column, the current flow is sometimes one way, sometimes the other.
Research on lightning will explain to you why.

The actual bolt itself may be plasma, but the current flow through it is definately one way at a time, so each "stroke" is DC, but the polarity can (and does) vary.

JW · « **Reply #5 on:** January 19, 2012, 09:28:58 PM »

okay, good tip.

gizmo · « **Reply #6 on:** January 19, 2012, 11:33:04 PM »

Quote from: rossw on January 19, 2012, 09:26:38 PM

The actual bolt itself may be plasma, but the current flow through it is definately one way at a time, so each "stroke" is DC, but the polarity can (and does) vary.

So doesnt that mean lightning is AC, since it flows in both directions? At one instant, it will be flowing in one direction, but at another instant, it could be flowing the otherway. AC power is DC at any one instant, isn't it?

If our conductor terminals are clouds and the earth, during a electric storm, the lightning is AC, as it would be flowing in both directions during the couse of the storm.

Are we talking lighning (AC), or a single lighning strike (DC)

Yes, a play on definitions, just for fun.

Glenn

rossw · « **Reply #7 on:** January 19, 2012, 11:53:09 PM »

Quote from: gizmo on January 19, 2012, 11:33:04 PM

Quote from: rossw on January 19, 2012, 09:26:38 PM
The actual bolt itself may be plasma, but the current flow through it is definately one way at a time, so each "stroke" is DC, but the polarity can (and does) vary.

So doesnt that mean lightning is AC, since it flows in both directions? At one instant, it will be flowing in one direction, but at another instant, it could be flowing the otherway. AC power is DC at any one instant, isn't it?

I am unaware of any instances where the polarity *within a single strike* changes.

Quote

If our conductor terminals are clouds and the earth, during a electric storm, the lightning is AC, as it would be flowing in both directions during the couse of the storm.
Are we talking lighning (AC), or a single lighning strike (DC)

What about cloud-to-cloud? It's a very complex series of potential differences. One cloud can discharge to another, which changes both THEIR potentials reference another cloud, or the ground. I'm hypothesising, but a bolt from cloud A to B, might change the potentials of the two clouds such that cloud A to ground will be a discharge ground-to-cloud, and cloud B will discharge cloud-to-ground!

bj · « **Reply #8 on:** January 20, 2012, 06:44:58 AM »

I'll bet a dollar that he still owes a dollar

electrondady1 · « **Reply #9 on:** January 20, 2012, 09:09:25 AM »

i actually saw a lightening strike last summer.
first time in my life .
i was driving home in a thunderstorm.
it was at the top of a hill, along a fence line.
less than 50 feet away, a bolt came down and enveloped a small tree.
it was like a column of plasma you could see into.
wild !

Norm · « **Reply #10 on:** January 20, 2012, 09:44:45 AM »

Quote from: bj on January 20, 2012, 06:44:58 AM

I'll bet a dollar that he still owes a dollar

beyond the shadow of a doubt
they always win
I'd bet a dollar too if I had it.....
(the Boss....she's got it all )

Norm.

SparWeb · « **Reply #11 on:** January 20, 2012, 11:01:17 AM »

I'd say it's "Neither" AC nor DC.

my 2 cents

(doesn't contribute much to the dollar you owe, though).

bj · « **Reply #12 on:** January 20, 2012, 04:45:33 PM »

Edady---saw the one that hit the shop last summer. (pure luck) Horrendous rain storm, lots of flashes,
and was looking out the window at the shop, thinking that it was a bit hard to see.(30 meters) Flash/crack,
and a fireball at the roof. Rest is history, but was interesting.

thirteen · « **Reply #13 on:** January 20, 2012, 09:35:55 PM »

I have had the miss fortune to be connected with lightening 4 times. Once I was tossed through a window into the house, once I was welding on a loader and it burnt my welder up and scorched my left hand and the loader burnt up, I was wiring in a conveyor and we had the cord stretched about to about 450 feet and it it and blew the cord end off that i was holding. the last time I was in a control tower and lightning hit the tower and destroyed all of the controls and blew two of the windows out. I lost three teeth and was goofy for about 4 days. I've seen it dance along the ground and I've watched as my nirghbors garage blew into little pieces.
No it is not fun and it hurts and it destroys some of your nerves and it takes weeks for your jionts to stop hurting. I still love to watch it.

Ding123 · « **Reply #14 on:** January 20, 2012, 11:14:58 PM »

Thirteen...you have just about the worst luck I have ever heard of! All that bad stuff happened to you , and i only last a dollar!I guessit wouldn't matter to you if it was AC or DC. Just wondering....

mab · « **Reply #15 on:** January 21, 2012, 12:23:57 PM »

Quote

I have had the miss fortune to be connected with lightening 4 times...

Is that why you're 'Thirteen'? it's just your 'lucky' number?

dinges · « **Reply #16 on:** January 21, 2012, 02:19:20 PM »

I think you can't argue with the fact that the cause (voltage difference) of a bolt of lightning is DC; it is static electricity, caused by built-up positive or negative charges. The charges can either be cloud vs. ground, or cloud vs. cloud. What little I know about it is that the vast majority, 'normal' polarity (forgot what that was for lightning) resulted in 'mild' bolts, whereas a reversed charge was more rare, but also caused the most spectacular lightning, with the differnce in kilo-amps by a factor 10; normal lightning, say, 10 kA peak, and 'reversed' lightning at 100 kA, roughly speaking.

Anyway, now to complicate matters a little bit more.... the cause of lightning may be DC, but the bolt of lightning (plasma) itself is a strong radio transmitter of amplitude-modulated RF, as can be heard on any medium-wave radio. So an effect of the discharge of the built-up charges results in RF (electromagnetic radiation, which is AC).

For example, the first radio transmitters were spark-gap transmitters; and the experiments Rudolf Hertz did in the late 19th century involved DC discharges between two spheres. Definitely DC that was the cause of the arc. But it also produced high-frequency AC.... the RF radiation that he wanted. Same can be seen in Tesla coils, where the AC of a spark gap is transformed to insanely high voltages. And you can only transform AC, not DC.....

Not saying I understand it, far from it. Was just pondering a little and thought to throw this out in the group. Curious what others can make of it.... DC producing (high-frequency) AC....

dinges · « **Reply #17 on:** January 21, 2012, 02:39:18 PM »

Quote from: JW on January 19, 2012, 09:04:20 PM

Remember you can use a welder to strike an arc with either AC or DC. You use AC to weld aluminum (gtaw) and electrode positive for steels.

Off topic, but a correction anyway:

Steel is normally TIG-welded with the electrode at a negative potential, not positive. This ensures most of the heat, about 70%, enters the workpiece and not the electrode. If you TIG-weld DCEP (DC, electrode positive), most of the heat would end up in the tip, very likely melting the pointed tip into a ball, causing a wandering arc that's hard to control.

The 'negative' side of the arc generates more heat than the positive side.

In stick welding with rutile electrodes, the electrode is also negative. Only some basic electrodes are used DCEP (just checked a pack of 7016).

JW · « **Reply #18 on:** January 21, 2012, 03:24:10 PM »

Quote from: dinges

Steel is normally TIG-welded with the electrode at a negative potential, not positive.

I think you may be right, although ive done tones of aluminum welding and not much steel, the biggest problem Ive encountered welding steel with straight argon, it should be c25.

I have welded stainless with AC and argon flux, but I was using a rare earth tungston.

JW

thirteen · « **Reply #19 on:** January 21, 2012, 06:19:47 PM »

As for thirteen being lucky or unlucky that is for you to think about. The number thirteen has followed me for all of my life. A quick short history. I was born early about 5 1/2 weeks and was flesh connected with my twin. I was in the hospital for thirteen days, I got to go back to Montana in 13 months I was 26 months old when I got my left leg burned I have had over the next several years a total of 13 operations on my leg to save it. I learned to walk on crutches and we lived on a corner street where one street was 3 the other was 1= 13. The house en umber was 39. The only dog i ever owned had 13 puppies. She passed away after having them. I was blown into the house with lightning at age 7 while I was trying to learn to run for I had been on crutch's for several years. When I was 10 I had three of my fingers get caught in swather while changing cutting blades= 13. My leg finally filled out and I started playing basket ball and football. My numbers were 26, 39, 65 divided by 13. My point average in basket ball was 13. I had my right hand cut and had to ware a cast for 13 weeks. My right leg got pierced with iron from a yard light that fell off a pole my dad and I were working on and it took thirteen stitches to seal it up. I had a road flare box blow up and i was partially blind for 13 days. The county I was raised in is no. 26 in the state. Take it or leave it this was done before age 14. There are many more things that have crossed my life with the number 13 attached to it. I have scares for the proof and joints that take time to move. I have been in plane wrecks train wrecks bus wrecks helicopter crashes crushed skull fractured pelvis seven fingers reattached The list goes on and on from 13 draft notices to 13 car wrecks that I have been involved with. Out of 39 graduating people in my class there are 13 of us left. I'm the guy that gets in a line and the paper runs out or the power goes out or their checks don't go thru. And there are hundreds of other things that over the years from falling to getting hit with electricity. I have defied the odds so far. Thirteen

Mary B · « **Reply #20 on:** January 21, 2012, 07:15:34 PM »

Dang! Stay away from me I don't need any accidents!

thirteen · « **Reply #21 on:** January 21, 2012, 07:42:14 PM »

at work if there are storms coming the other guy's won't work near me. If you get the right conditions a person can have St Elmos fire dance between your hands. Just static electricity but you can shock someone for fun. For my computor I have to run an extra ground or the screen distorts if I put my hands on it or near it. I have the same problem at work.

ETech · « **Reply #22 on:** January 21, 2012, 07:53:44 PM »

Actually, I think he's is very lucky!

To have all of that happen to you and still be alive.

May you have a less exciting remainder of you life.

ETech

oztules · « **Reply #23 on:** January 21, 2012, 08:39:04 PM »

Dinges.... DC spark to AC...

This is a guess at the process

With the DC we ionise the gas and direct energy into the resulting plasma. This energy lifts the energy level of the electrons in the valence bonds they were lying in before this happened. As they collapse back to their original energy levels, they emit photons (force carriers for electromagnetic force). These photons will be carrying the Electro Magneitc radiation for a lot of different frequencies... I suspect associated with defined quanta, and we could probably see a spectral analysis and play "pick the element/molecule".

Some of this EMR we can see as the bright light, and other frequencies we cannot see. Some higher energy than visible light (ultra violet), and some low energy in the RF band, and heat energy in the infrared band.
If the bolt is big...... there'll be lots of everything.

Of course there could be a much better explanation too.....

..............oztules

bj · « **Reply #24 on:** January 21, 2012, 10:32:22 PM »

Well, there is absolutley no doubt in my why you call yourself Thirteen. You have to be either the unluckiest
person, or the luckiest. I vote luckiest. You are still here.
May that luck hold for a good long time.

dinges · « **Reply #25 on:** January 22, 2012, 01:34:22 PM »

Quote from: oztules on January 21, 2012, 08:39:04 PM

With the DC we ionise the gas and direct energy into the resulting plasma. This energy lifts the energy level of the electrons in the valence bonds they were lying in before this happened. As they collapse back to their original energy levels, they emit photons (force carriers for electromagnetic force). These photons will be carrying the Electro Magneitc radiation for a lot of different frequencies... I suspect associated with defined quanta, and we could probably see a spectral analysis and play "pick the element/molecule".

Makes sense, Oztules. Excited atoms (who wouldn't be excited with a few million volts across him/her) emitting broad-band radiation. Yeah, probably a few spectral peaks from nitrogen, oxygen, hydrogen, etc.

So, to answer the original question, is lightning AC or DC: it would be *caused* by DC, but the resulting arc/plasma generates a lot of AC - up into the visible spectrum and beyond (UV).

I'm not exactly sure now who owes who a dollar.....

Peter (walks off humming AC/DC's 'Thunderstruck')

Mary B · « **Reply #26 on:** January 22, 2012, 03:28:39 PM »

It is the fast rise and fall time that generates the A/C and RF effects. Grounding my ham antennas takes some special precautions to protect against it.

oztules · « **Reply #27 on:** January 22, 2012, 04:28:43 PM »

Complete agreement sir Dinges...... DC causes the ionisation in the first place, and quantum mechanics can describe why the emissions are as they are i think.

Mary,
I think the fast rise and fall time has all to do with the dielectric breakdown under voltage pressure..... and running out of juice as soon as the gas turns plasma, and becomes a very very low impedance pathway/short circuit.

This in no way affects the AC emmissions. They are as a result of electrons being pushed up into a higher energy state..... from which they fall back from. The rest must by definition give up that energy in some form...... that form is electromagnetic radiation.

The frequency of that radiation will be a result of all the quanta energy levels that were available to accept that energy in the first place, in order to collapse and retransmit that energy at a wavelength that equates to that energy (quanta)..... so there will be a myriad of discrete frequencies emitted. The heat of the plasma may allow a lot of compounds to form, not all of which are stable, and all these things collapsing will generate their own spectral signature.... equivalent to the energy that got them there in the first place.

Sounds unnecessarily complicated...... but go away and find out how/why light finds it's way through some solids and semi solids (plastic, glass, mica etc) and not lead bricks, wood etc..... and you will see the same thing in action.

In fact, seeing any colour reflected off any object........ is the same thing again.... just shoving electrons up and down the energy level ladder... in discrete steps........frequency/colour.
Each frequency corresponds to a different discrete energy level (quanta)

If you think about a LED driven by a few DC volts, it excites the crystal, the electrons that were pushed into a higher level, collapse and retransmit that energy as a photon.
To us it looks like red or green etc light, but by choosing our crystal, we can get ultra violet, infra red or just about any other frequency.
Radio waves are only low frequency light waves..... so we excite the led with DC, and get an AC result shining back at us. Those light photons plus the heat given off must add up to the energy dissipation of the LED.

Nice to see you back Mr Dinges.

..............oztules

richhagen · « **Reply #28 on:** January 23, 2012, 02:58:57 PM »

Lightning is caused by a difference in potential between the ground and the atmosphere. Lightning is the movement of electrons to correct the inequality, so they will always be moving in either one direction or the other, making it a DC pulse. Once the electrons start to move, the electrical resistance in the air is reduced as the air mollecules convert to a plasma state which conducts electricity much better. Once that happens a large current can move between the atmosphere and the ground. Just my 2 cents. Rich

P.S. Good to hear from you Peter.

oztules · « **Reply #29 on:** January 24, 2012, 06:55:51 AM »

Agreed Rich... but where does the light come from then.... if not as I described???

..............oztules

richhagen · « **Reply #30 on:** January 24, 2012, 11:06:01 AM »

The same reason that a tungsten filament in an old fashioned incandescent lightbulb glows. Some of the energy of the electrons is converted to the random kinetic energy we know as heat or thermal energy in air molecules which causes the electrons to jump to higher orbitals, ionizing many of them, creating the plasma that cunducts the electrical current much better. When electrons fall back into orbits or from higher orbits to lower with the molecules, the difference in energy states of those orbitals is released via a photon. From the spectrum and intensities of light emmitted one ought to be able to tell the makeup of the gas too, as the specific energies are tied to the types of molecules and the specific differences in energy between different orbits. While you might have ac ripples on top, as you can hear the results on a radio at the time, but the bulk of the current to or from the ground depending on the polarity of the lightning will be DC as the current is conducted until the charges equalize to a point where the plasma conduit or lightning bolt if you prefer can no longer be maintained by the current passing through although often they seem to pulse bit as restrikes. At least this is how I currently understand it. I doubt we really disagree on this much, but I would have to say that lightning is basically DC although a pulsed DC current may have some similar effects to AC.

Rob Beckers · « **Reply #31 on:** January 26, 2012, 07:55:06 PM »

If anyone wants to learn more about lightning, and how to protect equipment from its effects:

http://www.solacity.com/Lightning.htm

I wrote this a while ago. It's a summary of many, many papers and other sources (and my own observations from blown wind inverters). A few experts reviewed it and deemed it accurate FWIW.

-RoB-

equiluxe · « **Reply #32 on:** May 19, 2012, 01:59:31 PM »

I think that you can consider the cloud and the earth as two plates of a capacitor. When you get a discharge it will go one way and then having reversed the charges will go the other at a very high rate every time loosing power all this at high frequency hence the rf. That is how spark transmitters work.

News:

Author Topic: Lightening? (Read 9023 times)