Reprint of papers on electrostatics and magnetism . m {q) hasbeen enlarged to bear also the in-sulating support (^) of the induction-plate. The outline of theinduction-plate falls within that of the quadrant beneath it by•16 of a centimetre (re of an inch) all round. It is distant 48of a centimetre (rw of an inch) from the upper surface of thequadrant. The dimensions in the figure are half full size. With an electrometer fitted with the induction-plate, theusual connexions for the first or direct method of measure-ment are the same as above mentioned. The electrode of theinduction-plate may be
Reprint of papers on electrostatics and magnetism . m {q) hasbeen enlarged to bear also the in-sulating support (^) of the induction-plate. The outline of theinduction-plate falls within that of the quadrant beneath it by•16 of a centimetre (re of an inch) all round. It is distant 48of a centimetre (rw of an inch) from the upper surface of thequadrant. The dimensions in the figure are half full size. With an electrometer fitted with the induction-plate, theusual connexions for the first or direct method of measure-ment are the same as above mentioned. The electrode of theinduction-plate may be connected with that of the quadrantbeneath it, or with the case, or it may be insulated, withoutsensibly affecting the indications of the instrument. Forthe second grade of sensibility the induction-plate is con-nected with the case, and the difference of potentials tobe measured is established between it and the distant pairof quadrants, the nearer pair being insulated by raising theirelectrode. To free the latter from the induced charge which. XX.] On Electrometers and Electrostatic Measicrements. 279 tHey commonly receive by the act of raising their electrode,a clisinsulator is provided, consisting of a light arm or springwhich may he turned so as to make contact with the quad-rant by means of a small milled head projecting above thecover. For a certain lower grade the arrangement is the same,except that the distant pair of quadrants, instead of the induc-tion-plate, is connected with the cover, and the difference ofpotentials to be measured is established between the cover andthe induction-plate. With this arrangement the deflectionsmeasure about five times the difference of potentials producingthe same deflectious by the second grade. The connexions may be further varied so as to produceother degrees of sensibility giving indications perfectly trust-worthy and available for comparative measurements. The dif-ferent methods of forming the connexions, with or without anind
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectmagnetism, bookyear18
