The outlines of physics: an elementary text-book . Jp---^ CQOunting a point uponany convenient conduct-ing body. The latter isto be placed upon an in-sulating plate and con-FiG. 201. nected by means of a wire with the terminals of the Toepler-Holtz machine. Theflame of a Rghted candle held near the point will bestrongly blown by the draft of air. (See Fig. 201.) The reaction of this convec-tion current takes theform of a backward thrustupon the point, and ifthe latter be mounted insuch a manner that it isfree to move, it will bedriven in the oppositedirection from that inwhich the current flow
The outlines of physics: an elementary text-book . Jp---^ CQOunting a point uponany convenient conduct-ing body. The latter isto be placed upon an in-sulating plate and con-FiG. 201. nected by means of a wire with the terminals of the Toepler-Holtz machine. Theflame of a Rghted candle held near the point will bestrongly blown by the draft of air. (See Fig. 201.) The reaction of this convec-tion current takes theform of a backward thrustupon the point, and ifthe latter be mounted insuch a manner that it isfree to move, it will bedriven in the oppositedirection from that inwhich the current phenomenon is illus-trated by means of theapparatus known as the electrical tourniquet (Fig. 202).This consists of two wires at right angles to one another,the points of which are bent as shown in the flgure. They. Fig. 202. ELECTRIC CHARGE UPON CONDUCTORS 243 are mounted upon a jeweled bearing at their commoncenter. When the tourniquet is charged from an electricalmachine, it revolves in the direction indicated by thearrow. 216. The Distribution of an Induced Charge. — The dis-tribution of charge upon bodies, discussed in the previousarticle, is that which exists when the charged body is notin the neighborhood of another electrified body. In thelatter case, the forces between the positive and negativecharges modify the character of the distribution. Imagine,for example, a small metal sphere which has not been elec-trified. The density of its charge is everywhere zero. Ifthis be brought into the neighborhood of a large con-ductor, positively charged, such as the prime conductor ofan electrical machine, it causes a charge by induction, asalready described (Art. 199). The portions of its surfacenearest the positively charged conductor will become nega-tively electrified, owing to the attractive
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishe, booksubjectphysics
