Sites: GlobalSpec.com | GlobalSpec Electronics | CR4 | Electronics360
Login | Register
The Engineer's Place for News and Discussion®

Previous in Forum: Applications for Synchronous Motors   Next in Forum: Differential Relays
Close

Comments Format:






Close

Subscribe to Discussion:

CR4 allows you to "subscribe" to a discussion
so that you can be notified of new comments to
the discussion via email.

Close

Rating Vote:







16 comments
Power-User

Join Date: Jan 2010
Location: BANGALORE, INDIA
Posts: 252
Good Answers: 5

Polarity of Lightning?

02/09/2010 12:55 PM

What is the polarity of lightning ? Is it positive with respect to ground, or is it negative or does it have both polarities or does it have an AC component- and if yes, what are the frequency components?

__________________
"Perplexity is the beginning of knowledge." -- Kahlil Gibran
Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Guru
New Zealand - Member - Kiwi Popular Science - Weaponology - New Member Engineering Fields - Power Engineering - New Member Engineering Fields - Electrical Engineering - New Member

Join Date: Sep 2006
Location: Auckland, New Zealand
Posts: 6298
Good Answers: 253
#1

Re: Polarity of Lightning?

02/09/2010 1:27 PM

Here is a good place to start.

http://en.wikipedia.org/wiki/Lightning

Also try an internet search for more information.

__________________
jack of all trades
Register to Reply
Anonymous Poster
#2

Re: Polarity of Lightning?

02/09/2010 3:56 PM

A custom-made Google Search, just for you.

Three Questions:

1. When you type http://www.google.com/ into your browser's address bar and then press the 'Enter' key, what happens?

2. Why are Indian user names on this forum so often spelled in ALL CAPS? Is a special, separate keyboard required for lower-case letters?

3. Did you know that ALL CAPS is almost universally recognized as the Internet equivalent of SHOUTING? (You don't have to shout your name. We can 'hear' you just fine.)

Register to Reply Score 2 for Off Topic
Anonymous Poster
#5
In reply to #2

Re: Polarity of Lightning?

02/10/2010 12:29 AM

What brought on this (to me seems unwarranted) tirade ? While apologising for all those Indians who only use caps, let me assure you that, by and large, we have better command over the English (and American too!) language than most others. May i request you to visit the websites of Pranav Mistry and Sixth Sense to see that Indians are well on the way to eliminate keyboards and mice ...

Register to Reply
Anonymous Poster
#8
In reply to #5

Re: Polarity of Lightning?

02/10/2010 1:14 AM

Dear Unnamed Indian,

Please do not generalize. The concern is serious and the professional communication need to be really professional... please note that this forum has members all over the world and the world expects good behavour from indians.. if you check the indian population and more so.. in engineering field.. very few indians top the scientists list..

so when putting forward your opinion on a few indian technologists who have made it to the top. don't generalize them with the engineers who have a minimal knowledge.. if an indian like Mr. Narayan Murthy of Infosys has made it to the tiop, then it doesn't mean that all indians can take credit for tat.. we need to work hard for that...

Register to Reply Off Topic (Score 5)
Guru
Hobbies - Fishing - New Member

Join Date: Jun 2006
Location: Rochester, NY
Posts: 867
Good Answers: 11
#10
In reply to #8

Re: Polarity of Lightning?

02/10/2010 8:37 AM

I have to agree with the folks from the Indian subcontinent that the tirade and disparaging comments along with the disingenuous directions to go to a reference site are, frankly, insulting. The fellow asked a question. If you don't have a polite answer - a real answer, not an insult to "check the wiki" (like your time is to precious to waste) - then SHUT UP!

and yeah, I was shouting....

__________________
Eric
Register to Reply
Anonymous Poster
#9
In reply to #5

Re: Polarity of Lightning?

02/10/2010 8:13 AM

we have better command over the English (and American too!) language than most others

Hate to bust your bubble, but there is no "American" language. Only English.

Funny story that my wife who grew up in NYC likes to tell about her grade school experiences where some kids often spoke in broken English or otherwise incoherently. And the nun would scold them by demanding that they "speak United States"

Register to Reply Score 1 for Off Topic
Guru

Join Date: Dec 2005
Location: Etats Unis
Posts: 1850
Good Answers: 44
#7
In reply to #2

Re: Polarity of Lightning?

02/10/2010 1:06 AM

Sounds like something LL would say.

__________________
The hardest thing to overcome, is not knowing that you don't know.
Register to Reply
Commentator
India - Member - Isloorkar

Join Date: Jan 2008
Location: Pune, India
Posts: 57
Good Answers: 3
#13
In reply to #2

Re: Polarity of Lightning?

02/26/2010 2:21 PM

26.2.10

ALL CAPS IS NOT ABOUT AN EGO TRIP OR WANTING TO GET NOTICED OR BEING NON CONFORMING.IT IS SIMPLY A MORE EFFICIENT TYPING DISCIPLINE. MOST OF US HAVE GRADUATED FROM DICTATING " WITH REF TO YR SO AND SO DTD SO AND SO" TO OUR STENOS/SECYS TO EMAILING AND NOW TEXTING.ALL CAPS FORMAT ELIMINATES REPEATED USE OF SHIFT KEYS.

ALL CAPS AND MISSED CALLS IN MOBILE TELEPHONY ARE TYPICAL INDIAN INNOVATIONS. THAT IS WHAT MAKES US SMARTER. SO THERE!

VINAY ISLOORKAR,PUNE INDIA

Register to Reply
3
Power-User

Join Date: Oct 2008
Location: Jakarta Indonesia
Posts: 123
Good Answers: 7
#3

Re: Polarity of Lightning?

02/09/2010 7:30 PM

Dear all,

Normally, thunder cloud top is positively and bottom is negatively charged. The surface of earth under the negatively charged cloud is induced as positive. Lightning flashes are in between negative cloud and positive earth. Lighting current is mainly DC with some AC components, the frequency range is DC to some hundred kHz.

In northern part of Japan, in winter season, there are lightnings between positive cloud and negative earth. The north wind form Russia, in high altitude, is so strong that the positively charged top cloud is separated form the negatively charged bottom. So, positively charged clouds land to Japan faster then negative.

Regards

__________________
Akihito Shigeno @ JGC-Indonesia
Register to Reply Good Answer (Score 3)
Anonymous Poster
#14
In reply to #3

Re: Polarity of Lightning?

02/27/2010 2:18 PM

So earth can be either positive or negative depending on the cloud cover?

Register to Reply
Power-User

Join Date: Oct 2008
Location: Jakarta Indonesia
Posts: 123
Good Answers: 7
#15
In reply to #14

Re: Polarity of Lightning?

03/02/2010 7:29 PM

Dear all,

Yes, if the cloud above you is negatively charged, ground beneath you will be charged positively, because opposite charge attract each other.

Regard.

__________________
Akihito Shigeno @ JGC-Indonesia
Register to Reply
Power-User

Join Date: Jan 2010
Location: BANGALORE, INDIA
Posts: 252
Good Answers: 5
#4

Re: Polarity of Lightning?

02/09/2010 10:36 PM

Thanks so much for enlightening me on this. So depending on areas the lightening can be positive or negative and it does have some high frequency components too. The link reference to a website is very useful.

__________________
"Perplexity is the beginning of knowledge." -- Kahlil Gibran
Register to Reply
Guru

Join Date: May 2007
Location: Geelong, Australia
Posts: 1089
Good Answers: 54
#6

Re: Polarity of Lightning?

02/10/2010 12:40 AM

I'd think that a lightning strike would be a pretty good approximation to a dirac impulse. Looking up fourier transforms will show the sort of frequency spectrum you'd expect (basically DC to RF)

__________________
If there's something you don't understand...Then a wizard did it. As heard on "The Simpsons".
Register to Reply
Guru

Join Date: Nov 2006
Location: OH USA
Posts: 538
Good Answers: 24
#11

Re: Polarity of Lightning?

02/10/2010 10:42 AM

Statistically, worldwide over 90% of all cloud to earth lightning strokes are of negative polarity, with a mean first stroke magnitude of approximately 35,000 amperes. Although the stroke waveform is sometimes described as DC it is more accurately an impulse with a rapidly rising front and a longer tail. That waveform for positive and negative polarity impulse tests in the laboratory to simulate lightning is defined as 1.2/50, meaning a time from 0 to peak of 1.2 microseconds and a time to half crest on the tail of the wave of 50 microseconds. The front time is actually measured by the slope of the rise time between 10% and 90% of crest or peak value. That is done because the front waveform is generally not a sharply defined shape. The slope described defines virtual zero time and from that time, the time to crest and time to half crest on the tail is established. If you are interested in further details, you might refer to ANSI/IEEE Std 4 "Techniques for High Voltage Testing", or the IEC International or National Standard equivalent.

The composition of a cloud to earth lightning stroke is also interesting. It typically initiates with a pilot streamer, followed by a step leader then a return stroke (which is the visible part). The total duration of the majority of strokes (including restrikes) is a fraction of the time to crest of one half cycle of power frequency voltage.

Positive polarity strokes tend to be higher in current magnitude and although most strokes are described as high current, short duration there can also be strokes that are of lower current with longer duration. LCLD strokes are generally the most damaging and are responsible for most lightning caused fires.

Register to Reply Score 1 for Good Answer
Power-User

Join Date: Jan 2010
Location: BANGALORE, INDIA
Posts: 252
Good Answers: 5
#12
In reply to #11

Re: Polarity of Lightning?

02/10/2010 10:59 AM

Thank you so much for your very highly technically informative explanation.

__________________
"Perplexity is the beginning of knowledge." -- Kahlil Gibran
Register to Reply
Power-User

Join Date: Jan 2010
Location: BANGALORE, INDIA
Posts: 252
Good Answers: 5
#16

Re: Polarity of Lightning?

03/02/2010 11:26 PM

Basically I was looking for some inputs for me to develop and design a very novel insulator. I thank forum members for a wonderful brain storming. I did get what I was looking for. Now the polarity - really does not matter. My novel insulator can handle both polarities.

__________________
"Perplexity is the beginning of knowledge." -- Kahlil Gibran
Register to Reply
Register to Reply 16 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Copy to Clipboard

Users who posted comments:

a+x=z (3); Akihito Shigeno (2); Anonymous Poster (5); Bluestone (1); ca1ic0cat (1); ffej (1); isloorkar (1); jack of all trades (1); rcapper (1)

Previous in Forum: Applications for Synchronous Motors   Next in Forum: Differential Relays
You might be interested in: Lightning Protection Systems, Power Frequency Converters, RF Frequency Converters