From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Investigation into subsidiary sparks and the effects of earthing a tube acting as a condenser.
| Identifier | ExFiles\Box 61b\4\ scan0195 | |
| Date | 22th May 1919 guessed | |
| -3- Contd. induced in it of sufficient magnitude to enable one to draw sparks from it nearly 1/8" long. The outer tube is acting with the principal wire as a condenser, and the other wires are raised to potentials of the same order as that tube. The sparking on the subsidiary gaps is, in this case, somewhat brighter than previously. We found very distinctly that by earthing the tube, either with a wire or by gripping it when standing on the ground, that we could, to a very great extent, get rid of the subsidiary sparks altogether. It is quite true that it is still possible to get very tiny subsidiary sparks about of the same magnitude as in condition (1). The effect of earthing the tube is to increase the capacity of the condenser system, and therefore to lower the induced potential of the tube itself, and of the subsidiary wires to a lesser degree; at the same time the sparking potential of the main spark is slightly reduced and its intensity increased owing to the condenser action. The tube used was of mild steel 31.25" long i.d. 1.00" o.d. 1.20". We could not detect any difference whether we earthed one end of the tube or the other, or earthed it in the centre by hand; but, having one end of the tube earthed we could produce a slight spark, between the earth and the wire connected to the other end, which certainly did go out when the main spark was out out by increasing its gap, and which effect would, therefore, appear to be a true electromagnetic effect. This, however, is a very much smaller effect than the electrostatic. Contd. | ||