Alternate Current Measurement . hird column gives the correspondingvalues of 50A or the ampere turns associated with the 50-turn Thevalue of K was known with fair accuracy, and was due to various parallelcombinations of condensers which had been tested by ballistic methods;some months previously. The half microfarad condenser used with the- 1908.] Alternate Current Measurement. 341 -500-turn coil for the moving coil circuit caused a small magnetising currentround the field windings. The values given for K represent the capacitiesactually connected with the 1000-turn coil, and these shou
Alternate Current Measurement . hird column gives the correspondingvalues of 50A or the ampere turns associated with the 50-turn Thevalue of K was known with fair accuracy, and was due to various parallelcombinations of condensers which had been tested by ballistic methods;some months previously. The half microfarad condenser used with the- 1908.] Alternate Current Measurement. 341 -500-turn coil for the moving coil circuit caused a small magnetising currentround the field windings. The values given for K represent the capacitiesactually connected with the 1000-turn coil, and these should be eachincreased by 0*5/4 or 0125 microfarad to get numbers proportional to theampere turns due to the condenser currents. Table I. K. 50A. A. K. 50A. ainperes. mf. amp. turns. amperes. mf. amp. turns. 3-1 o-o 155-0 0-70 4*33 35-0 2-16 1-58 108-0 0-85 5-02 42-5 2-2 1-62 110-0 1-0 5-35 50-0 183 2*0 91-5 1-70 6-64 85-0 1-69 2-33 84-5 1-87 6-93 93-5 1-28 3-02 64-0 2-79 8*55 139-5 0-95 358 47-5 3-23 8-97 161-5 0-93 3-62 46-5. o 468Capacity in -microfarads. Fig. 9. 10 342 Dr. W. E. Sumpner. [Jan, 21 The results are shown plotted in fig. 9. When the current A has value, reference to fig. 7 will show that A is in phase with thereactive voltage. Hence the power wasted in the core may be obtained bymultiplying the minimum number of ampere turns, 35, by 0*080 the voltageper turn round the core. This power works out to be 2*8 watts for 80-cycle-circuits for the induction density corresponding with this frequency and0*080 volt per turn. The loss thus obtained agrees closely with othermeasurements which have been made upon the core losses of the electro-magnet in question. A more convenient method of testing one of these instruments for thecapacity Kc needed for compensation is (see fig. 10) simply to put the fieldcoil in series with the moving coil and to apply various condensers-It to the terminals of the field coil only, when a constant voltage V isapplied to
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