The outlines of physics: an elementary text-book . Fig. 212. 223. The ftuadrant Electrometer. — For the experimentshitherto described, the gold-leaf electroscope is sufiSciently 1 Dielectric: the name applied to any material through which electro-static induction takes place. CONDENSEBS 263 sensitive. It is possible, however, to construct instru-ments of far greater delicacy. One of the most useful ofthese is the quadrant electrometer. It con-sists of a thin sheet of aluminium, called / ^^__.^^ \the needle which is shown in Fig. 213. I ^—^ /This is suspended by means of two par- j.^^ 213.^^^al
The outlines of physics: an elementary text-book . Fig. 212. 223. The ftuadrant Electrometer. — For the experimentshitherto described, the gold-leaf electroscope is sufiSciently 1 Dielectric: the name applied to any material through which electro-static induction takes place. CONDENSEBS 263 sensitive. It is possible, however, to construct instru-ments of far greater delicacy. One of the most useful ofthese is the quadrant electrometer. It con-sists of a thin sheet of aluminium, called / ^^__.^^ \the needle which is shown in Fig. 213. I ^—^ /This is suspended by means of two par- j.^^ 213.^^^allel fibers of unspun silk attached to aplatinum wire which passes through the center of theneedle. To the other end of this wire, which extendsbelow the needle, is attached a tiny vane of platinum.(See Fig. 214.) The needle hangs in the middle of aflat, cylindrical box of brass which is oiitt diametricallythrough in two directions, and is thus divraed into quad-rants (Fig. 215). These quadrants are slightly separated. Fig. 216, Fig. 21a. from one another, and are mounted upon glass posts whichserve as insulators. A glass jar below has an outer coatingof foil like a Leyden jar. Within, it is partly filled with 254 THE OUTLINES OF PHYSICS strong sulphuric acid. This is placed at such a heightthat the vane v attached to the needle dips into the 216 shows the arrangement of a simple form of aquadrant electrometer. A small mirror, m (Fig. 214), is attached to the plati-num wire above the needle. By means of the direction inwhich it reflects a beam of light thrown upon it, everymovement of the needle is indicated. To use the electrometer, the acid within the jar ischarged by means of the electrophorus. The charge isshared by the needle, since the latter is in contact with theacid through the* platinum wire and vane. The positionof the needle mthin the box is shown by the dotted linein Fig. 216. If two opposite quadrants as aa, or bb, begiven a small charge, the needle
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishe, booksubjectphysics
