# Measuring Lightning

## Electrical Engineers and Meteorologists Devise Method to Measure Strength of Lightning Strikes on Tall Buildings

September 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.

## Science Insider

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.

The American Mathematical Society,the Mathematical Association of America, the American Meteorological Society, the Institute for Operations Research and the Management Sciences, and the Institute of Electrical and Electronics Engineers, Inc., contributed to the information contained in the TV portion of this report.

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To Go Inside This Science:
University of Florida
Gainesville, FL
rakov@ece.ufl.edu, 352-392-4242

American Mathematical Society
Providence, RI 02904-2294
1-800-321-4267

Mathematical Association of America
Washington, DC 20036-1358
1-800-741-9415

American Meteorological Society
Boston, MA 02108-3693
617-227-2425

Institute of Electrical and Electronics Engineers, Inc.
IEEE
IEEE-USA
Pender McCarter
p.mccarter@ieee.org

Institute for Operations Research and the Management Sciences
Barry List
443-757-3560
barry.list@informs.org