Monday, November 16, 2009

LIGHTNING RODS DISCHARGE THE CLOUDS?


Make a model "landscape", install some lightning rods on the tiny houses, then bring a "storm cloud" nearby: bring the metal sphere of a VandeGraaff Electrostatic generator over your small town. The strong electric charge on the sphere will vanish. Doesn't this prove that lightning rods can discharge a thunderstorm? Nope.
The above demonstration was thought at one time to be accurate, and this old mistake is still in many books. In reality, lightning rods cannot remove the charge-imbalance from a thunderstorm. The scale of the typical demo is wrong. The stormcloud is a few miles up, and a few miles across, yet the lightning rod on the house is only a few feet tall. Therefore the metal-sphere "cloud" should be fairly large, and "Rod" should be far less than 1mm tall and attached to a wide metal ground plate.
The typical demonstration doesn't illustrate a lightning rod, it illustrates a 2000-ft radio tower or extremely tall office building.
Think about it: how can a tiny needle affect cubic kilometers of strong e-field? How could the relatively tiny current from a metal rod discharge a cloud that's over 1KM away. It can't! To do so, it would have to emit a hurricane wind made of ionized air. Unfortunately the lightning rod on your roof only emits about the same current as the needle in the model town: it emits a few microamperes. In other words, the scale model is not correct because the current coming from the needle is way too high. In order to be at the proper scale, the current would have to be hundreds of thousands of times smaller; too small to affect the VDG machine's charge.

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