ELECTRICITY IN CARS.

Hawera Star, Volume XLVII, 12 November 1927, Page 15

ELECTRICITY IN CARS.

POSSIBLE DANGERS. Definite evidence lias been obtained from time to time that a car can become charged with static electricity, which may be non-teehnically defined as ‘‘electricity at rest.” To the scientist the condition is a specially interesting one, and it is certain that much has yet to be found out concerning this remarkable phenomenon. At the outset it should be made clear that the static electrification of a car lias nothing to do with the electrical equipment or its operation. A circumstance which accounts for much is the fact that a ear is electrically insulated from the earth by its rubber tyres, provided these are in a dry state. A recent instance, which is vouched for by the “Motor,” England, is that of a car becoming so highly electrically charged by brake fiction as to cause a very smart shock accompanied by a snapping spark on touching the brake drum. Here is /bn interesting instance of the ‘onservation of mechanical energy’ by friction between metal and fabric into a powerful static charge, and it is probably a very frequent- condition in the ordinary everyday use of a ear. ‘Sonic few years ago a largo car was dc-stroved by fire when filling up with petrol.’ The owner stated that he saw i mvsterious spark jump across the tank’ opening to the funnel when fill ng up, and this caused ignition of the octroi*. Only a static charge could ac•ount for it.

Another remarkable tact is that such phenomena may easily arise from atmospheric electricity. It is a wellmown fact that the atmosphere, even it no greater height than an ordinary wireless aerial, is at times so highly charged with static electricity as t'O cause sparks and shocks on touching the terminals of a crystal site. The inference is that a large metal mass such as a car must necessarily often become charged by induction from an dectical atmosphere, and even to so high a potential in a dry atmosphere is to give rise to sparks and severe shocks. So far as the petrol tire risk is concerned, if such conditions arise, the only real precaution is to “earth” the tank thoroughly by means of a wire connecting it to a water pipe or other well-earthed metal object, and -hereby discharge the static electricity before any petrol is poured in.