Electricity for public schools and colleges . rubber acquires an equal — charge. The +ly excited glass, its charge kept from leakage by theflap of silk, next comes opposite to the conductor with its row ofsharp points. On the conductor it acts inductively, repelling +and attracting — charge. This — electricity is discharged, by con-vection currents of charged air, from the points on to the glass ;so that this latter passes on in its original unexcited + charge is left on the prime conductor, to be utilised. Use of putting the rubber to earth.—\\^ have seen that the 62 ELECTRICITY
Electricity for public schools and colleges . rubber acquires an equal — charge. The +ly excited glass, its charge kept from leakage by theflap of silk, next comes opposite to the conductor with its row ofsharp points. On the conductor it acts inductively, repelling +and attracting — charge. This — electricity is discharged, by con-vection currents of charged air, from the points on to the glass ;so that this latter passes on in its original unexcited + charge is left on the prime conductor, to be utilised. Use of putting the rubber to earth.—\\^ have seen that the 62 ELECTRICITY CH. IV. glass surface returns to the rubber in a neutral, or nearly neutral,condition. But the rubber was left charged —. Hence, if theoriginal separation of + or — were to go on, then after some turnsthe rubber would become highly — charged, and the tendency topart with some of its — charge to the glass would at some point inthe process at last balance the tendency to excite the glass + would come to a t IG. 11. But if we put the rubber to earth, we shall get the initial con-dition of the rubber maintamed by a steady passage of — electricityto earth. Later on we shall treat of this matter from a potentialpoint of view. So, if the prime conductor be put to earth, we can use therubber as a source of — electricity. If the rubber and conductor CH. IV. SIMPLER PHENOMENA OF ELECTROSTATICS 63 both be insulated, but they be riearly connected by conductingrods, when we turn the cyhnder we shall see a series of sparksbridge over the gap left; the + charge of the conductor and the— charge of the rubber continually neutralising each other. II. The common plate machine.—In this there is nothing es-sentially different from the cylinder machine. A glance at thefigure will explain all. There are generally two rubbers ; and in this form of machinethey cannot well be insulated if required ; so the machine cannotbe used as a source of both -h and
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Keywords: ., bookcentury1800, bookdecade1890, bookpubl, booksubjectelectricity
