Just getting out of your car seat can create a voltage on your body of 15,000 volts or more - enough to give you a noticeable shock, says physicist Dr John Chubb. At the Institute of Physics Annual Congress in Brighton, Dr Chubb will be describing experiments he has carried out with his own car to help the development of better car seat materials.
Electric charge builds up whenever two materials are separated.
Usually this charge leaks away almost immediately to Earth via anything in contact with the ground. If the voltage is high enough, you get a spark across the gap from the material to Earth, causing a shock or even an explosion if flammable gases are present. If you also happen to be filling the car with petrol and there is petrol vapour about, then there is a very small but real risk that a spark from you could cause ignition. At present, not much is known about which kinds of car seat material work best to keep the body voltage below the level of 3.5 kV at which a shock is felt. Dr Chubb will be describing the results of tests he has carried out at his company premises in Cheltenham, wearing various kinds of everyday clothing and using an ordinary car with its seats covered by different kinds of trial fabrics.