Sunday, 6 September 2009
Way In, Way Out
The two termini of a discharge are at different potentials. The higher, or positive, potential is at the anode, while the lower, or negative, potential is at the cathode. These electrodes are often conductors, but need not be. In a thunderstorm, a cloud electrode may simply be a region of excess charge distributed over a volume. These names were given by Michael Faraday, with the help of the classical scholar William Whewell, when he began to study electrochemistry and electrical discharges in the 1830's. The word "anode" is from the Greek "aná-hodos" or "way in," while "cathode" is from "katá-hodos," or "way out." Electrode is a later creation for "electro-hodos" or "electric way," and is noncommttal as to the positive direction of the current.