Elements of Physics for Use in Secondary Schools (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1894 Excerpt: ...from the point. The last two experiments give meaning to the names "disruptive discharge" and " convective discharge." The latter takes place from points. These favor the rapid and quiet discharge of electricity. Indeed, a body having pointed projections cannot retain a charge. St. Elmo's fire is but a convective discharge, of the variety called "glow" discharge, which takes place from or towards the pointed masts of ships. Exp. 173.--Hang two pith balls by silk threads so that one touches the outside and the other the inside of a tin can. Support the can on the positive pole of electrical machine and electrify it. The ball on the outside is repelled, while that on the inside is unaffected. Static electricity "resides" on the outside of a hollow conductor, so that a hollow conductor has the same capacity or "will hold" as much electricity as a Fig. 130. solid one of the same outside diameter. When the electricity "flows," however, the solid conductor conducts better, the "current" not being confined to the surface. Exp. 174.--Repetitional Experiments. Place a wig on a metallic head and electrify. Why do the hairs stand on end? (6) Ignite gas jet between the poles of the electrical machine, (c) Ignite ether placed in shoal glass or porcelain dish, (d) Mount on point of steel needle two crossed, sharpened wires flattened at center by hammering, and bent at the four sharpened ends like tubes of Barker's mill. Connect needle with positive pole. The "Electric Whirl" is the name of the apparatus, (e) Cut a large number of diamond-shaped pieces of tinfoil about one centimeter long. Fasten them in a spiral upon the outside of a freshly varnished tube, so that they nearly but not quite t...