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ShareSeptember 1, 2008 — Electrical engineers developed a mathematical equation to measure the electrical current strength of lightning as it strikes tall buildings. The researchers developed new ways to prepare estimates of current, based on the location that experiences the highest current. The method accounts for the way waves of current reflect within a building and can interpret several different situations depending on where the peak current occurs on the building.
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Florida is the lightning capital of the U.S., followed by Texas, North Carolina, Ohio and New York. More people die from lightning than tornadoes and hurricanes, and most people don’t realize they can be struck by lightning even when the center of a thunderstorm is more than 10 miles away. Now, engineers are using a new, improved way to keep you safer when a storm strikes.
Jessica Lynch was taping a storm when she was hit. She wasn’t seriously hurt -- but that’s not the case for everyone. Lightning can carry an electric potential of more than 100 million volts and a current as strong as 100,000 amps. Now, compare that to your entire house, which only needs 200 volts and 220 amps.
Measuring lightning's power can be difficult. Traditionally, lightning is measured by detection strikes on flat ground, but in the lightning lab at the University of Florida, electrical engineer Vladimir Rakov, Ph.D., found a way to more precisely measure lightning’s current strength on tall buildings.
"Initially, there will be two waves or pulses propagating in opposite directions from the tower top," says Dr. Rakov. "Each of those two waves will contribute to the magnetic field measured by the lightning detection network."
Current measurements on the ground are larger than at the actual strike point on a building. By developing a new mathematical equation, Dr. Rakov can now better determine lightning strength and provide better lightning protection for buildings and power lines -- which helps to keep us all safer.
"You calculate how many outages you will have per year and then you can decide if you can live with that number of outages, or if you should invest more money in lightning protection," Dr. Rakov says.
And remember, when you see lightning, go inside. Even inside, talking on the phone is the leading cause of lightning injuries. Standing under a tall tree is the most dangerous place to take shelter. And if you don’t think lightning strikes the same place twice -- think again.
"This is not true … I know this for sure!" Dr. Rakov says. "Tall buildings are definitely struck by lightning multiple times, even during the same thunderstorm."
The odds of becoming a lightning victim in the U.S. in your lifetime is one in 3,000; and here’s something you may not have known -- most Florida lightning strikes that result in death happen on Wednesdays. It’s not clear why.
The American Mathematical Society, the Mathematical Association of America, the American Meteorological Society, the Institute of Electrical and Electronics Engineers, Inc., and the Institute for Operations Research and the Management Sciences contributed to the information contained in the TV portion of this report. contributed to the information contained in the TV portion of this report.
WHAT IS LIGHTNING? Lightning is a form of static electricity. We experience static electricity every time we drag our feet on a carpet and then touch a conducting surface, like a metal doorknob. The shuffling causes our bodies to pick up extra electrons. Touching something with a positive charge, like metal, causes the electrons to "jump" across the small gap from our fingers to the object, and we experience a tiny electric shock. Similarly, lightning occurs because clouds become negatively charged as the water droplets inside rub up against each other during the natural process of evaporation and condensation, when moisture accumulates in the clouds. This charge seeks out something with a positive charge -- the ground, ideally -- and the lightning is the "spark" closing the gap between the two.
As more and more water droplets collide inside a cloud, the friction between them produces enough extra energy to knock off electrons. The ousted electrons gather at the lower portion of the cloud, giving it a negative charge. Eventually the charge becomes so intense that electrons on the Earth's surface are repelled by the growing negative charge and burrow deeper into the Earth. The Earth's surface becomes positively charged, and hence very attractive to the negative charge accumulating in the bottom of the cloud. All that is needed is a conductive path between cloud and Earth, in the form of ionized air -- another byproduct of the collision process. When the two charges finally meet, current jumps between the earth and the cloud, and the result is lightning.
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