Display lights in the clouds followed with a booming voice that often occurs when heavy rains. Most people are surprised by a flash of light and sound. They soon find shelter because they know the level of danger. Not infrequently the lightning bolt singe stem trees, the human body, and cause power grid outages. That's a little picture of the magnitude of lightning and thunder.
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| Lightning from the tops of cumulonimbus cloud. (Picture from: http://science.howstuffworks.com/) |
Lightning is a natural phenomenon long observed existence on earth. However, until now scientists did not know exactly how lightning happens, or how they interact with the upper layers of the atmosphere or the electro-magnetic field that exists on earth.
The process of generating lightning until now still being debated by scientists theme. Various theories and investigations carried out in an attempt to more clearly reveal about lightning and matters related thereto.
The first stage is the formation of thunder clouds gathering in charge. The theory generally accepted about how to obtain the charge cloud to produce lightning is static electricity theory. Beginning with moist steam rising into the clouds, and then developed into small water droplets or ice crystals. Ice crystals collide, then there was a transfer of electrons. Electron transfer is due to friction between the colliding particles, so that the different charges (positive and negative charge) separately and assembled in the cloud.
It is not yet determined exactly how the charge listed in the clouds. However, there is the hypothesis that the upper cloud region contains a strong positive charge, the central region cloud contains a strong negative charge, and the lower cloud region contains a weak positive charge.
The difference of the charge in the second area of the clouds pose a potential difference or voltage. If the potential difference between the two regions is large enough there will be a release of negative (electrons) charges to achieve balance in the cloud system. The process of discharge is called lightning. Lightning usually occurs in the form of two-stroke. In the first strike, the negative charge flows from the cloud to the ground. This is not a very bright flash. A number of branching lightning can usually be seen spreading out from the main flash point. When the first bolt of lightning strike the ground, lightning currents both positively charged lightning is formed from the first line and go directly to the cloud. The difference in electric voltage between the cloud and the ground surface exceeds several million volts.
Flashes very quickly formed down to earth with a speed of 96,000 miles per hour. The first lightning reaches the Earth's surface within 20 milliseconds, and struck the opposite direction to the cloud within 70 microseconds. Overall, the lightning lasted about half a second.
The sound of thunder that follows the lightning caused by sudden heating the air around the path on lightning. The air becomes expand at speeds exceeding the speed of sound even though the waves kejutnya return to normal sound waves in the range of a few meters.
The power of lightning from thousands amperes to 200,000 amperes or equal to the power needed to light pieces of 100 watt light bulb. Meanwhile, the light released by lightning brighter than the light of 10 million pieces of 100 watt light bulb.
The temperature at the point where the lightning is formed to achieve 10,000 degrees Celsius and the heat generated by the smallest lightning can reach 10 times that. This incredible hot show that lightning can easily burn and destroy all the elements that exist in the Earth's surface.
The appearance of lightning can occur within a cloud, between two clouds, and from clouds to the ground. Type of lightning is the most common lightning in a cloud (intracloud) with a quota of about 90 per cent of the total types of lightning. Type of lightning occurs within the cloud can not be seen through ordinary observation. Meanwhile, a bolt of lightning that comes from the cloud to the surface of the earth is the most common type of lightning visible.
In addition to the type of lightning that releases negative charge (from the negatively charged cloud), there is also a kind of lightning that release positive charges to the surface of the earth. Type of this lightning is positive, because out of the tops cumulonimbus cloud containing ice crystals are positively charged. The emergence of positive lightning tour begins with a lightning bolt coming out of the positively charged cloud tops in a direction nearly horizontal at a distance so far away from the parent thunderstorm (cumulonimbus), then finally turned abruptly and spread down vertically to the surface of the earth.
The researchers showed that positive lightning strikes typically have a strength of six to ten times more powerful than negative lightning, the length of ten times longer than negative lightning, and can be grabbed at a distance of tens of kilometers of storm clouds thunder (cumulonimbus). The difference in voltage at the positive lightning must be very larger because of the lightning bolt must be running at a great distance from the cumulonimbus cloud.
Positive lightning average carrying amount of electrical current which can reach 300 kiloampere or about ten times more than negative lightning, drain charge that could reach 300 coulombs, potential difference up to 1 gigavolt, discharge energy of 300 gigajoules, and appeared within hundreds of milliseconds. *** [DEDE NURROSYID | PIKIRAN RAKYAT 06122012]
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