The Boy Mechanic, Volume 1: 700 Things for Boys to Do · Chapter 558Detector for Slight Electrical Charges
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Aluminum Foil in a Bottle
A thin glass bottle is thoroughly cleaned and fitted with a rubber stopper. A hole is made through the center of the stopper large enough to admit a small brass rod. The length of this rod will be governed by the shape of the bottle, but 3-1/2 in. will be about right. The bottom of the rod is bent and two pieces of aluminum foil, each about 1/4 in. wide and 1/2 in. long, are glued to it. The two pieces of foil, fastened to the rod, are better shown in Fig. 2. Fasten a polished brass ball to, the top of the rod, and the instrument is ready for use. Place the article which you wish to test near the ball, and if it holds a slight electrical charge, the two pieces of foil will draw together. If it does not hold a charge, the foils will not move.
Transcriber's note: The foil pieces will move apart, not together.
Contributed by Ralph L. La Rue, Goshen, N. Y.