Lightning #2 – The Physics of Lightning
The Physics of Lightning:
Direct current electricity. ( DC, not AC like the current that feeds our houses.)
Very high voltage and high amperage: can exceed 100 million volts, 100,000 amps.
Very hot, 50,000C, hotter than the surface of the sun.
Very short duration – instantaneous; milliseconds.
Produces Ozone, O3, that protects the earth from the deadly effects of ultraviolet light.
Electricity travels over the surface of objects, unless there is an internal conductor.
Internal conductors – nerves & blood vessels (contain an electrolyte solution).
Formation of lightning:
Vertical acceleration of moist air, forms ice crystals, causes charge separation.
Areas of positively and negatively charged atoms occur throughout the cloud head.
Electrical discharge to stabilize charges created in cumulonimbus clouds.
The base is negatively charged with a positive shadow forming on earth.
Typically, lightning occurs under and along the leading edge of the cumulonimbus cloud.
It can occur as far as 10 miles away, a strike “out of the blue.”
Can travel horizontally over 60 miles; the longest recorded to date was at 118 miles long.
Lightning strike can be:
Direct strike or streamer current.
Splash or surface arc.
Step voltage or ground current.
The principle is don’t be a conductor!
For more detailed information about lightning and lightning-related injuries see the Wilderness Medicine Newsletter, Lightning – Beauty & the Beast, July/August 2003.
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