. A text book of physics, for the use of students of science and engineering . employed will onlyindicate a rise or a fall of potential,^without measuring it. The electroscope, .however, has been made into an instru-ment capable of fair accuracy formeasuring potentials by Mr. C. T. The leaf of gold, or aluminium D, issupported by a wire (Fig. 882) andconnection can be made between itand the conductor E by means of apiece of wire carried by a spring. Ondepressing E, the wire comes into con-tact with the wire supporting the leaf,making metallic connection. The tubecarrying the conducto
. A text book of physics, for the use of students of science and engineering . employed will onlyindicate a rise or a fall of potential,^without measuring it. The electroscope, .however, has been made into an instru-ment capable of fair accuracy formeasuring potentials by Mr. C. T. The leaf of gold, or aluminium D, issupported by a wire (Fig. 882) andconnection can be made between itand the conductor E by means of apiece of wire carried by a spring. Ondepressing E, the wire comes into con-tact with the wire supporting the leaf,making metallic connection. The tubecarrying the conductors is insulated byan ebonite plug. The leaves are sur-rounded by the brass box A, having acircular window through which they areobserved by a short-focus telescopehaving a finely divided scale in theeyepiece. The position of the image of the leaf on the eyepiecescale indicates the potential of the leaf. It is necessary, however,to calibrate the scale by applying known potentials and noting theitions of the leaf, before any readings of potential can be madeby the Fig. 882.—The Wilson electroscope. QUADRANT ELECTROMETER 947 Quadrant electrometer.—For accurate measurement of small>otentials the quadrant electrometer is much superior to the gold-eaf electroscope. This consists of four hollowuadrants AABB (Fig. 883) with a paddle-haped conductor C (sometimes called theneedle ) hanging within them. This paddles carried by a wire support W to which amall concave mirror is attached, the whole>eing suspended by a quartz fibre. Thisrrangement enables the deflection of the>addle to be observed, exactly as in thease of the reflecting galvanometer (p. 864).n Fig. 884 the arrangement of a quadrant„_ electrometer is shown
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishe, booksubjectphysics
