. Popular electricity magazine in plain English. Fig. 74. Electrostatic Volmeter is taken up by a spring. The motion of thisspring-is transmitted to an indicating pointerthrough a small drum over which a cord instrument has some very good is no induction since the wire is notformed into coils. It is not sensitive to rapidfluctuations, hence is dead beat. Electrostatic Voltmeters: Another class ofvoltmeter suitable for alternating current workis one which depends on the attraction or re-pulsion of two surfaces carrying electrostaticcharges. They are generally employed
. Popular electricity magazine in plain English. Fig. 74. Electrostatic Volmeter is taken up by a spring. The motion of thisspring-is transmitted to an indicating pointerthrough a small drum over which a cord instrument has some very good is no induction since the wire is notformed into coils. It is not sensitive to rapidfluctuations, hence is dead beat. Electrostatic Voltmeters: Another class ofvoltmeter suitable for alternating current workis one which depends on the attraction or re-pulsion of two surfaces carrying electrostaticcharges. They are generally employed for meas-uring unusually high voltages. The type in-vented by Lord Kelvin is shown in Fig. The fixed quadrants (aa) and (bb) aremounted so that the aluminum vane (w)swings between them on the pivot (d). Thequadrants are connected to one side of the cir-cuit and the swinging vane to the other, so thatwhen they become charged, the vane is attractedand drawn in between the quadrants and thevoltage indicated by thepointer. This type ofinstrument requires nopower whatever for itsoperation. Wattmeters: The in-strument most common-ly used for measuringpower is called a watt-meter. There are twotypes in common use;the moVing-coil-fixed-coil type and the induc-tion type. Fig. 75 shows Fig. 75. Moving-coil-fixed-the principle of opera- coil Wattmeter tion of the first type. In Fig. 75 the line is connected in series withthe fixed coils which consist of a few turns ofheavy wire. The moving coil is connected acrossthe line. The strength of the magnetic field isproportional to the strength of the current flow-ing through the fixed coils, therefore is propor-tional to the line current. T
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectelectri, bookyear1912
