Electrical measurementsA laboratory manual . y,then the third term in the equation of electromotiveforces drops out and where / and E are either maximum values or the squareroots of the mean squares, as measured by an electro-dynamometer. If the circuit contains capacity but no self-induction,then 7: V R. Q-ai Further, if the resistance of the circuit is zero, This last equation furnishes an independent methodof measuring the capacity of a condenser. 112. Measurement of the Capacity of an Electro-static Voltmeter.^ — The voltmeter isihst employed to measure the potentialdifference e between th
Electrical measurementsA laboratory manual . y,then the third term in the equation of electromotiveforces drops out and where / and E are either maximum values or the squareroots of the mean squares, as measured by an electro-dynamometer. If the circuit contains capacity but no self-induction,then 7: V R. Q-ai Further, if the resistance of the circuit is zero, This last equation furnishes an independent methodof measuring the capacity of a condenser. 112. Measurement of the Capacity of an Electro-static Voltmeter.^ — The voltmeter isihst employed to measure the potentialdifference e between the alternatingmains. A non-inductive graphite resist-ance of several megohms is then joinedin series with the voltmeter. It willnow indicate a smaller potential differ-ence 60- This potential difference isone-quarter of a period behind thecharging current, while the potentialdifference e^ between the terminals ofthe graphite resistance agrees in phase ^Dr, Sahulka, in the Proceedings of the Chicago International ElectricalCongress^ p. SELF-INDUCTION AND MUTUAL INDUCTION. 241 with the current, since this resistance r is non-inductiveand without capacity. Hence (Fig. Ill) e = s/~~f^2. Therefore e^ maybe computed and /equals — . Then since I also equals ^ e., 127rnr Example. The alternating current had 2500 full periods per minute. Hence oj=2nn = 262. The table gives the results with a Kelvin multicellalar volt-meter. The values of r are in megohms, the potential differencein volts, the current in millionths of an ampere, and the capacityin millionths of a microfarad. r e ei 69 i C 122 112 103 The capacity was greater for the higher values of 62 than forthe lower ones, because the movable system is deflected so as toincrease the capacity of the instrument as an air condenser for thehigher readings. 113. Measureme
Size: 1063px × 2352px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, bookpublisherbosto, bookyear1895
