There are many good explanations of lightning which cover the mechanics behind the various processes. We can recommend a few sources depending on just how deep you'd like to get...One terrifically entertaining source of info is written by Dr. Uman. However, if you're just browsing to get a quick insight without getting blinded with science, then this is the place...
Let's get a few slightly technical definitions out the way first, which should help in the understanding!
Storm cell
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We see this as the cloud where the lightning originates from. It's where lightning's electrical charge is generated
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Electrical Charge
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Let's think of this as stored electrical 'energy'.
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Current
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Is the flow of electrical energy. |
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Laymans' Lightning...
In a nut-shell, 'lightning' is the transfer of electrical current from the source (storm cell) to or from another object. Check out http://lecglobal.com/learn/lightning-101/charge-transfer/
This could be to/from another cloud (cloud-to-cloud), a tree, a structure or the earth itself.
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Image of cloud-to-cloud strike. |
What we tend to see is not the initial strike as this happens far too quickly for the naked eye (220,000km/h), but what we see is the 'return stroke', which is the equalising return current back to the source cell.
Check out the latest 'clip of the month'...
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What's the risk?...
A key point to learn is that lightning is a 'competitive event'. That is, there are several factors in the mix that determine whether you (or your building) will be struck, for example, Proximity - the closer to the storm cell (cloud) you are, the greater the field intensity, the greater the risk.
The degree of exposure or 'isolation' also plays a vital role. For example, if your building sticks out like a sore thumb with little cover from surrounding trees or buildings, then the greater the risk you are providing the best competitive conditions for a strike.
Part of BS EN 62305:2 has a fairly comprehensive RISK ASSESSMENT, which can quantify what your vulnerability is both in terms of external risk (damage, fire, death) and internal risk (sparking, surge, etc.).
Click on our Request a Risk Assessment above for a more detailed assessment.
Check out the latest 'clip of the month'...to see what can happen.