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Tuesday, December 16, 2008

Cars and Lightning

Listening to Leo LaPorte's radio show (via podcast), called "The Tech Guy." Fella just called in about his car getting hit twice in a minute or so by lightning. Leo brought up the old, mistaken assumption that cars are protected because of the rubber tires. Not particularly so., and I'm surprised Leo didn't catch that. Maybe he didn't want his listener to feel foolish?

Cars are (or have been) protected, not by the rubber tires, but by the steel bodies. With the massive voltages involved, wet rubber doesn't do that much, and certainly cars can and will be struck by lightening. The conductive body of the car does provide a better path to ground than the surrounding air, so the lightning is more likely to travel through the car than the air. Same with aircraft, even though they "aren't grounded." A path travelling through the body of the aircraft is electrically easier than a path through air, even wet air. Above and below the aircraft, the lightning is travelling through air, of course.

So, how are cars protected? Well, the metal box inside which you're sitting is lots more conductive than you are. The car's body acts as what's called a Faraday Cage. So the lightning is much more likely to travel through the metallic car body and around the human passengers.

And now I'm wondering -- cars are now made out of non-metallic materials, cause they're cheaper. Do cars still adequately protect their passengers from lightning?

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