Lightning noises

[Siamsal]

I was watching a storm last night.

One particular lightning stroke was very close (frighteningly close!). I thought I heard a little 'zzzzzz' noise, like sparking electricity, quite faint, then a fraction of second later, the 'crack'. Which frightened me to death, it was so close and loud.

Would the 'zzzzzz' actually happen, or am I imagining it?!

[teag1rl]

I dont think you imagined the zzzzz. Even if it wasnt the lightening itself it could be the electricity around you. Um, I'm not a weatherman though!

[Clanad]

Sure... you get the same reaction and noise (with some crackling as well) when standing under a high tension electrical transmission line(s). They, too, transmit about 250KW to 350KW, about the same as an average bolt of lightning produces...

[SteveSxx]

Clanad - don't know where you get these figures from
10 to 120 million volts is the average voltage on a lightning bolt.......

[Siamsal]

But why the (small) delay between the zzzzzz & the crack?

[SteveSxx]

Because the lightning probably struck very close to you and the sound (crack) came from a distance away - ie half way up the strike

[lightoftruth]

You live in the midlands. We had a big lightning storm here in derby and me being the nutcase that i am went out into the garden in the thick of it and pulled up a chair and just sat thru it and just watched the lighniing. Got very wet but it was very cool

[BillyBB]

Fantastic storm last night LOT, was in Derby at the time. Not seen one like it for ten years.

[Clanad]

This, from numerous websites, SteveSxx: The energy contained in a single lightning stroke can power a 100 Watt light bulb for 90 days, which is equivalent to 215 kWh (kilo-Watt hours).
This is the full URL for this article... http://www.lightningtalks.com/lightningfacts.h tm

Maybe that you're talking Volts and I'm speaking of watts as a reference... Thanks!

[Catso]

But shouldn't the crack & the zzzzz be coincident? You could say the zzzzz came from halfway, as well.

[Siamsal]

Yes, I live north of Derby.

I'me half convinced SteveSxx, but surely at least part of the 'crack' would have been very close to me, as close as the 'zzzzz' was.

Does it take a finite amount of time for the air to be heated enough to make the 'crack', I wonder.

I would guess the delay between the two was around � second.

[chakka35]

Your units are all in a jumble, Clanad (and hello again in a different context!). Kilowatts are a measure of power and kilowatt-hours a measure of energy.
It isn't clear what you mean when you say that an overhead line 'transmits' 250KW of power. You cannot mean along its length otherwise we would be in darkness most of the night. If you mean by radiation into the space around it then over what length, at at what voltage?
For a (say) 50 megavolt lightning strike to generate only 250 kilowatts the current involved would be only 50 milliamps! Hardly the sort of current to fell trees or cause severe burns in animals.

[chakka35]

Correction to my last: I meant 5 milliamps.