The lightning phenomenon

August 16, 2009Santosh 2 Comments »

Lightning: A giant discharge of electricity accompanied by a brilliant flash of light and a loud crack of thunder. The discharge can occur between the cloud and the ground, other clouds, or within a single cloud. The electric field within the storm is much stronger than the one between the storm base and the earth ‘s surface, so about 75-80% of lightning occurs within the storm cloud (which never reaches the ground). The spark is only about 1-2 inches in diameter but can reach over five miles (eight kilometers) in length, raise the temperature of the air by as much as 50,000 degrees Fahrenheit (27,700 degrees Celsius), and contain a hundred million electrical volts. One thing is for sure,when that discharge of electricity occurs from clouds to the ground, you don’t want to be in that path ! Although most of us relate lightning to the thunderstorms, it’s been seen in volcanic eruptions, extremely intense forest fires, surface nuclear detonations, heavy snowstorms, and in large hurricanes as well.

What causes it?
The creation of lightning is a complicated process. We generally know what conditions are needed to produce lightning, but the exact way a cloud builds  up the electrical charges that lead to lightning is not completely understood. Convection theorists believe that a moving thunderstorm gathers  positively charged particles along the ground that travel with the storm. Bottom parts of clouds contain negatively charged particles. As the differences in charges continue to increase, positively charged particles rise up tall objects such as trees, houses, and telephone poles—and people. The negatively charged bottom part of the storm sends out an invisible charge toward the ground. When the charge gets close to the ground, it is attracted by all the positively charged objects, and a channel develops. The subsequent electrical transfer in the channel is lightning. Lightning in turn balances the charges and it stops within fraction of a second. The thunder is a bi-product of the lightning. Thunder is the sound caused by rapidly expanding gases along a channel of lightning discharge. Energy from lightning heats the air to 20-50,000 degrees Fahrenheit. This causes a rapid expansion of the air, creating a sound wave.

Some facts about lightning and precautions to take:
1. Each second there are 50 to 100 Cloud-to-Ground Lightning Strikes to the Earth world-wide.
2. Most lightning strikes average 2 to 3 miles long and carry a current of 10000 Amps at 100 million Volts.
3. Thunder can only be heard about 12 miles away under good quiet outdoor conditions.
4. Lightning can kill people or cause cardiac arrest. Injuries range from severe burns and permanent brain damage to memory loss and personality change. About 10 percent of lightning-struck victims are killed, and 70 percent suffer serious long-term effects. About 400 people survive lightning strokes in the U.S. each year.
5. You can get struck by lightning even when the center of a thunderstorm is 10 miles (16 kilometers) away and there are blue skies overhead.
6. If your hair stands up in a storm, it could be a bad sign that positive charges (in the ground) are rising through you, reaching toward the negatively charged part of the storm. Your best bet is to get yourself immediately indoors.
7. The threat of lightning continues for a much longer period than most people realize. Wait at least 30 minutes after the last clap of thunder before leaving shelter. Don’t be fooled by sunshine or blue sky!
8. Inside homes, people should stay away from windows and doors and avoid contact with anything that conductselectricity, including land line telephones.
9. Surge protectors do not protect against direct lightning strikes. Unplug equipment such as computers and televisions.
10. A house or other substantial building offers the best protection from lightning. For a shelter to provide protection from lightning, it must contain a mechanism for conducting the electrical current from the point of contact to the ground. These mechanisms   may be on the outside of the  structure, may be contained within the walls of the structure, or may be a combination of the two. On the outside, lightning can travel along the outer shell of the building or may follow metal gutters and downspouts to the ground. Inside a structure, lightning can follow conductors such as the electrical wiring, plumbing, and telephone lines to the ground.
11. A shelter that does not contain plumbing or wiring throughout or some other mechanism for grounding from the roof to ground is not safe. Small wooden, vinyl, or metal sheds offer little or no protection from lightning and should be avoided during thunderstorms.
12. Avoid contact with cement concrete walls, which contain metal reinforcing bars.
13. Avoid using washers and dryers, since they have contacts with the plumbing/water and electrical systems.
14. Rubber shoes will not give you any meaningful protection from lightning.
15. A car (with a metal top) can offer you some protection – but keep your hands from the metal sides.
16. Always avoid being the highest object anywhere—or taking shelter near or under the highest object, including tall trees. Avoid being near a lightning rod or standing near metal objects such as a fence or underground pipes.

If someone is struck:
1. If a person is struck by lightning, medical care may be needed immediately to save the person’s life. Cardiac arrest and irregularities, burns, and nerve damage are common in cases where people are struck by lightning.
2. With proper treatment, including CPR if necessary, most victims survive a lightning strike.
3. Victims of lightning do not retain the charge and are not “electrified.” It is safe to help them.

It will be nice to get struck by the lightning and then live to tell about it, isn’t it ? But then on one of these days, may be not !! 😉

Most of the information on this page was adapted from the NOAA’s National Weather Service’s Lightning Safety Web site. The animation image was taken from the wikipedia website.

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