Science Questions

Sun, 28th May 2006

Part of the show Naked Science Q&A and the Science of Happiness


Neil in Felixstowe asked:

Why do some people suffer so badly with static electric shocks? It's particularly bad when I get out of my car.


The whole planet is engulfed in a dense blanket of air molecules and as your car drives along it has to push those air molecules out of the way. The reason a car makes a noise as it goes along is because it's creating turbulence and making air molecules bash against each other and the car and that sort of ripples away. What this means is that static charge builds up on the car because it's isolated from the road. This is because most cars have rubber tyres and rubber is a good insulator. It's a little bit similar to when you have a storm cloud and want some lightning. You've got lots of water molecules and little ice crystals called hydrometeors. The wind currents inside the clouds bash these things around and as they slowly rub against each other they transfer charge. You end up with a cloud that has one charge at the top of the cloud and the other charge at the bottom of the cloud and that's why you get a lightning bolt. So it's sort of doing a similar experiment with your car at road level. When you step out of the car, the car body carries a charge and you are connected to the ground. You are also isolated from the car and so when you then touch the car to close the door, then the charge difference between you, the ground and the car neutralises itself using you as the vehicle by which to do that. People who wear rubber soled shoes will get these shocks worse than people who don't because you can't earth yourself to the ground as well.


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