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Hey, Matt:

The power lines along the park corridor are incredibly noisy. As a physics major in school, I know that noise requires energy, and this means these high-tension lines are losing a lot of energy. Is there something wrong with them, or are they just operating normally? I once had occasion to find my brother-in-law's house in Long Beach by listening for the noise, because I remembered that his house was located in an area with particularly annoying power line buzzing.

-- Ash Raiteri, the net

Let's say the situation is normally abnormal. That frying-bacon sound is a product of corona discharge. When you push high-voltage electricity through cable, it ionizes a thin layer of nearby air (through electron release, oxygen is transformed to ozone). A byproduct of ionization sometimes is noise or even a visible bluish glow. Damp, foggy air and dirty power lines are the best breeding grounds, so the closer you are to the ocean the more of a problem it would be. That also explains why power companies periodically do something as apparently senseless as hose down the lines.

Corona discharge is just one small contributor to energy loss between the point of generation and your wall plug. Sending electricity through a transmission line over long distances is like trying to herd cats. It will take any tiny opportunity to leak out or transform itself into something else. Estimates vary, but perhaps 18 to 20 percent of generated energy never makes it all the way to your electric toothbrush. From 5 to 8 percent is in transmission losses like corona discharge. Most lines are sending AC current, which is less efficient than DC but has other advantages in terms of power generation and voltages levels.

On the other hand, when the principle of corona discharge is controlled and packaged, you can whap on a price tag and sell it as a life-enhancing negative-ion generator or air purifier or antibacterial swimming pool cleaner or wound-healing device. If you scan the recent lit, corona-discharge technology is to the year 2000 what magnetic corsets were in 1900 -- the newest cure-it-with-electricity fad. Science looks at most of these claims with a raised eyebrow, though there are industrial applications where it is useful.

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