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Thread: Lightning @ NUS

  1. #41

    Default Re: Lightning @ NUS

    Quote Originally Posted by Del_CtrlnoAlt View Post
    think...

    1) u suddenly ground strike... so u mean, 1 lightning strike, all on ground die?

    2) so ground strike no one is spared?

    3) so u mean, lightning strike, air become super static electricity and all mankind gets wiped out?
    1) i already told you in what cases will people be spared.

    2) i already told you in what cases will people be spared.

    3) answering this would be a waste of time.

  2. #42
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    Default Re: Lightning @ NUS

    Quote Originally Posted by satay16 View Post
    1) i already told you in what cases will people be spared.

    2) i already told you in what cases will people be spared.

    3) answering this would be a waste of time.
    1) i already told u that u will get flamed

    2) i also told u u get flamed more

    3) have a nice day...
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  3. #43

    Default Re: Lightning @ NUS

    Quote Originally Posted by Del_CtrlnoAlt View Post
    1) i already told u that u will get flamed

    2) i also told u u get flamed more

    3) have a nice day...
    .................

    no fun.

    but seriously, ground strikes kill more people then direct hits, but due to the positions of the people at the instant of lightning strike, some (actually most) are spared.

  4. #44

    Default Re: Lightning @ NUS

    oh oh, here's a video clip i found:

    http://www.youtube.com/watch?v=LzjXbd-WcHI

    as you can see, some get hurt, but some dun(even though they are close together). chances are that those who got hurt had two feets on the ground that time, causing a voltage gradient to be present across their feet. those who did not had one leg on the ground that instant(cos they were running). there's also the possibility that those unharm fellows had both feets equidistant from the strike, but that is pretty unlikely, considering the rapid movement of them during soccer.

    edit: get the idea about ground strikes? it wasn't raining that time, they were wearing shoes, and............soccer players are not super conductive.
    Last edited by satay16; 29th March 2007 at 01:09 PM.

  5. #45

    Default Re: Lightning @ NUS

    keep note that at 00:07, the middle guy did not get hurt during the strike. notice that he had only one foot on the ground that instant.

  6. #46

    Default Re: Lightning @ NUS

    I guess Physics and Maths Calculations wont help much in such situations !! Luck does..

  7. #47

    Default Re: Lightning @ NUS

    Quote Originally Posted by Qingkai View Post
    I guess Physics and Maths Calculations wont help much in such situations !! Luck does..
    yeah. true actually. but the least you could do is hop around with one foot.

  8. #48

    Default Re: Lightning @ NUS

    woah. amazing. see number of cows killed in strikes.
    http://search.yahoo.com/search?p=cow...utf-8&fr=b2ie7

  9. #49
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    Default Re: Lightning @ NUS

    Quote Originally Posted by satay16 View Post
    woah. amazing. see number of cows killed in strikes.
    http://search.yahoo.com/search?p=cow...utf-8&fr=b2ie7
    err no... so how many killed?
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  10. #50
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    Default Re: Lightning @ NUS

    Quote Originally Posted by satay16 View Post
    woah. amazing. see number of cows killed in strikes.
    http://search.yahoo.com/search?p=cow...utf-8&fr=b2ie7
    btw... so u think they are well done, medium rare or raw when it strikes them?
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  11. #51

    Default Re: Lightning @ NUS

    Quote Originally Posted by Del_CtrlnoAlt View Post
    btw... so u think they are well done, medium rare or raw when it strikes them?
    none. they are alive when it strikes them.

  12. #52
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    Default Re: Lightning @ NUS

    Quote Originally Posted by satay16 View Post
    none. they are alive when it strikes them.
    so how, is the steak tender?
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  13. #53

    Default Re: Lightning @ NUS

    Quote Originally Posted by Del_CtrlnoAlt View Post
    so how, is the steak tender?
    erm......... dunno. need apparatus to measure its young modulus first.

  14. #54
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    Default Re: Lightning @ NUS

    yoyoyo... chilled out man...
    no need to get so excited about lightning.
    You are who you are. Shoot what you enjoy.
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  15. #55

    Default Re: Lightning @ NUS

    Quote Originally Posted by mojopy View Post
    yoyoyo... chilled out man...
    no need to get so excited about lightning.
    lighting is one of the most important aspects in photography. of cos it is exciting.

  16. #56

    Default Re: Lightning @ NUS

    Quote Originally Posted by satay16 View Post
    *beep* wrong.

    so what if you are grounded? the lightning did not strike on his head.

    when lightning strike the ground, the point it strike has the highest potential difference as compared to earth's 0 voltage. due to resistance of the ground, when you get further and further away from the point of lightning strike, voltage decreases, like a pattern of concentric circles. so, if both feets are on the same equipotential lines, there isn't any potential difference across the feet, therefore, no current will flow. if one leg is on the ground, better still, cos it would be like connecting the positive terminal of a battery back to the positive terminal of the same battery, aka, still no potential difference.

    but if the feet and point of lightning strike are collinear, it means that both feet are stepping on different equipotential lines. this causes a potential difference across the feet. how large is the potential you might ask. very very large. reason being the ground is of relatively high resistance, and the rate of decrease of potential is proportionate to the ground's resistance. so, it means that a small change in distance can cause a large potential difference. so, now, it becomes like having a few thousand volts of electricity across both feet, the further the separation of the feet, the more lethal the shock.

    this is why sometimes, when you see those lighning accidents in soccer matches, you noticed that only some players get hurt even though the others are close to them. this is the explaination why. you might ask why they dun teach about this in lightning preventioan class. the thing is you dunno where the lightning can hit, so the best deal is to actually lie on the ground, cos you will then become part of the ground. though the distance separation is large, every point on your body is at the same potential as the ground, therefore, no harm done.

    btw, this is also the explanation of why cows always(or mostly) die in lightning strikes. i mean, erm...........look at the separation of their front and hind legs.

    and nope, i did not get this infomation from any website. what for? it is all logical thinking. lazy to google or wiki.
    sorry bro, but i have to disagree with you. i have been working high voltage lines for almost 20 years and know all about potential difference. Bottom line, lightning is trying to get to get to ground and if you are on the ground one foot two feet whatever, you are a path to ground. you can argue all you want from a text book but i worked it in theory and in a practical sense. i'm sorry but your tech explanations don't do much for me except try to hide a partial understanding of a topic...one foot two foot...explain to me a ground rod then which can have a diameter of 5/8 inch which is meant to take electricity to ground and sticks out of the ground roughly 18 inches. that 5/8 inch diameter is smaller than a big toe and has only one point on the ground...so tell me now does it matter one foot or two? seperation of limbs means nothing if you are grounded...key word grounded. if you are grounded or are in the path between electricity and ground you will get shoked...end of story and maybe end of life.

    i know you're probably going to argue this just for the sake of arguing, but really, if you work on high voltage lines for roughly 20 years and the first 7 of those are spent in night school after work 3 days a week for 2 hours a night (more class-time for one subject than any uni will give) that is solely devoted to electricity you would not be saying how far apart a cows legs are determines if it lives or dies in a lightning strike. there are so many other factors to consider, resistance, ions, air, moisture, but bottom line, the bolt is still looking for a path to ground.

    why do i bother to challenge you in this...because some CSer is going to take pictures of lightning standing on one leg thinking he or she is safe. as for lying on the ground, you have just given yourself more surface area for lightning to hit and if you are saying you are safe because you are the same potential as the ground...think again...lightning is trying to get to ground and that potential difference, that same potential difference you just made yourself a part of...any electrician knows that you don't even have to be grounded to get shocked...you just need a difference of potential. so if you want to create a difference of potential that is the same as the ground by lying on it...then be my guest. but again, potential difference means more in a closed circuit than it does in an open or shorted curcuit.

    i see some guys knocking you and NUS in this thread. i don't know you personally but i really hope these are not the things being taught there or anywhere. at the end of the day, a path of least of resistence or a path to ground is what electricity will follow. remember a grounded conductor is different from a grounding conductor, both have a purpose and if lightning bolts were not trying to get to ground, why would they be hitting objects that are grounded then? grounded, it's about being grounded, not the potential difference...people, please be safe and give responsible advice. i might not know how to take the best pictures, but i know electricity

    do spires or lightning rods on building have a potential difference or are they grounded and provide lightning bolts with a path to ground? it's to provide a path to ground at a higher point then the building to attract the lightning to it rather then the building itself. now tell me...would a building have more of a potential difference then a rod that sometimes only sticks up 2 feet or even less from a building and a pathetically small surface area in comparison to a building? the building has a far greater potential difference. however lightning will 99.9% of the time hit the rod because it is the highest point that is grounded...again, keyword grounded; just like a cow in a open pasture, or just like a person on one foot or two.

    your analysis of standing on a foot and it being like a positive terminal and how it will protect you...i think you are confusing a closed circuit as to an open one. again, we are talking ground here and ground in a circuit causes a short of the circuit. that's why they call it a short circuit, because it didn't follow the complete circuit. in a short circuit you see sparks and hear a boom, just like little lightning, but that's what lightning does...it does not follow a circuit like in our homes, it makes it's own direct path or direct short, and it is looking for a path to ground. cows, one foot two feet people included. again...if you are grounded, that's it!

    my basis for this arguement is for the safety of photogs not just for the sake of arguing who knows more or throwing out big words. seriously, one of the first things you learn is that electricity tries to get to ground, so where does all this potential difference come in? we are not talking batteries and electricity in the home that is on a circuit and needs potential difference or a load to be useful. we are talking free and wild electricity that is not on a circuit and is looking for ground.

    anyways prove me wrong if you feel you need to or if i am, but keep CSers safety in mind when you do it.


  17. #57

    Default Re: Lightning @ NUS

    Quote Originally Posted by Hawaiisg View Post
    sorry bro, but i have to disagree with you. i have been working high voltage lines for almost 20 years and know all about potential difference. Bottom line, lightning is trying to get to get to ground and if you are on the ground one foot two feet whatever, you are a path to ground. you can argue all you want from a text book but i worked it in theory and in a practical sense. i'm sorry but your tech explanations don't do much for me except try to hide a partial understanding of a topic...one foot two foot...explain to me a ground rod then which can have a diameter of 5/8 inch which is meant to take electricity to ground and sticks out of the ground roughly 18 inches. that 5/8 inch diameter is smaller than a big toe and has only one point on the ground...so tell me now does it matter one foot or two? seperation of limbs means nothing if you are grounded...key word grounded. if you are grounded or are in the path between electricity and ground you will get shoked...end of story and maybe end of life.

    i know you're probably going to argue this just for the sake of arguing, but really, if you work on high voltage lines for roughly 20 years and the first 7 of those are spent in night school after work 3 days a week for 2 hours a night (more class-time for one subject than any uni will give) that is solely devoted to electricity you would not be saying how far apart a cows legs are determines if it lives or dies in a lightning strike. there are so many other factors to consider, resistance, ions, air, moisture, but bottom line, the bolt is still looking for a path to ground.

    why do i bother to challenge you in this...because some CSer is going to take pictures of lightning standing on one leg thinking he or she is safe. as for lying on the ground, you have just given yourself more surface area for lightning to hit and if you are saying you are safe because you are the same potential as the ground...think again...lightning is trying to get to ground and that potential difference, that same potential difference you just made yourself a part of...any electrician knows that you don't even have to be grounded to get shocked...you just need a difference of potential. so if you want to create a difference of potential that is the same as the ground by lying on it...then be my guest. but again, potential difference means more in a closed circuit than it does in an open or shorted curcuit.

    i see some guys knocking you and NUS in this thread. i don't know you personally but i really hope these are not the things being taught there or anywhere. at the end of the day, a path of least of resistence or a path to ground is what electricity will follow. remember a grounded conductor is different from a grounding conductor, both have a purpose and if lightning bolts were not trying to get to ground, why would they be hitting objects that are grounded then? grounded, it's about being grounded, not the potential difference...people, please be safe and give responsible advice. i might not know how to take the best pictures, but i know electricity

    do spires or lightning rods on building have a potential difference or are they grounded and provide lightning bolts with a path to ground? it's to provide a path to ground at a higher point then the building to attract the lightning to it rather then the building itself. now tell me...would a building have more of a potential difference then a rod that sometimes only sticks up 2 feet or even less from a building and a pathetically small surface area in comparison to a building? the building has a far greater potential difference. however lightning will 99.9% of the time hit the rod because it is the highest point that is grounded...again, keyword grounded; just like a cow in a open pasture, or just like a person on one foot or two.

    your analysis of standing on a foot and it being like a positive terminal and how it will protect you...i think you are confusing a closed circuit as to an open one. again, we are talking ground here and ground in a circuit causes a short of the circuit. that's why they call it a short circuit, because it didn't follow the complete circuit. in a short circuit you see sparks and hear a boom, just like little lightning, but that's what lightning does...it does not follow a circuit like in our homes, it makes it's own direct path or direct short, and it is looking for a path to ground. cows, one foot two feet people included. again...if you are grounded, that's it!

    my basis for this arguement is for the safety of photogs not just for the sake of arguing who knows more or throwing out big words. seriously, one of the first things you learn is that electricity tries to get to ground, so where does all this potential difference come in? we are not talking batteries and electricity in the home that is on a circuit and needs potential difference or a load to be useful. we are talking free and wild electricity that is not on a circuit and is looking for ground.

    anyways prove me wrong if you feel you need to or if i am, but keep CSers safety in mind when you do it.

    AHHH!!!!!!! I GOING TO SAY THIS JUST ONE MORE TIME!!!!!!!!!!!!!! I AM NOT TALKING ABOUT DIRECT HITS!!!!!!! I AM TALKING ABOUT GROUND STRIKES!!!!!!!!!!!!! OMG!!!!!!!!!!!
    Last edited by satay16; 29th March 2007 at 08:03 PM.

  18. #58

    Default Re: Lightning @ NUS

    COME COME COME!!!!! I GOING TO DRAW OUT A DIAGRAM OF A DIRECT HIT AND A GROUND STRIKE!!!



    SEE THE DIFFERENCE?!!!!!!!


    omg.............

  19. #59

    Default Re: Lightning @ NUS

    Quote Originally Posted by satay16 View Post
    oh oh, here's a video clip i found:

    http://www.youtube.com/watch?v=LzjXbd-WcHI

    as you can see, some get hurt, but some dun(even though they are close together). chances are that those who got hurt had two feets on the ground that time, causing a voltage gradient to be present across their feet. those who did not had one leg on the ground that instant(cos they were running). there's also the possibility that those unharm fellows had both feets equidistant from the strike, but that is pretty unlikely, considering the rapid movement of them during soccer.

    edit: get the idea about ground strikes? it wasn't raining that time, they were wearing shoes, and............soccer players are not super conductive.

    errr so what does that clip prove...man let me see, people that actually get struck are smoking, burnt, and other things. these guys, none of that why? hmmm, i saw a flash that generates heat and will scare the crap out of you...but no bolt hitting anything. where on the field did the lightning strike? i dun see any mark? or maybe was it an overhead strike that the lightning suppression systems built in stadiums and light poles intercepted but was still close enough to scare these guys and give them a headache, perhaps minor burns or hot air that they breathed in that can hurt their lungs or cause other internal discomfort?

    i've seen a lot of heavy high voltage explosions and although none ever hit me direct, it took some time for me to shake it off just because i was close to it and it scares the sh*t out of you. I would even sit out for a bit wondering if i was okay...just like these guys. so i could imagine how a much stronger lightning flash would be. maybe a stray did hit the field or the player, then again maybe not, i saw nothing conclusive either way. regardless, i apologize for saying this, but i think you really should stop giving people false info bro because your theories literally are standing on only leg.


    life is an experience that does not only come from a book

  20. #60

    Default Re: Lightning @ NUS

    okokok...calm down.............calm............calm............ let me explain my case dear 20 years experience high voltage cable guy.

    this is my case for a ground strike, repeat, ground strike

    ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike ground strike

    ok. that should be enough.



    when your feet are equidistant away from the point of strike, they are standing on the same equipotential line. eg, position A. since there isn't any voltage gradient, no current flows through the legs, meaning, no harm.

    but if the feet and point of strike are collinear, it means that the feet are standning in different equipotential lines, creating a voltage gradient. therefore, ZAP!!! current flows through them.

    for the case of a cow, their legs are even further, therefore creating an even larger voltage gradient, a even more deadly one. i did some simple calculations. around a one foot interval, the change in potential can amount to few thousands volts(so the numbers i put in my diagram are kind of off, but the idea is there).

    get it?
    Last edited by satay16; 29th March 2007 at 08:22 PM.

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