grover: paraffined paper condensers 277 



ELECTRICITY. — The capacity and phase difference of paraf- 

 fined paper condensers as functions of the temperature and 

 frequency. Frederick W. Groyer. Communicated by 

 E. B. Rosa. To appear in the Bulletim of the Bureau of 

 Standards, 7: No. 4. 1911. 



In an ideal condenser the capacity would be independent of 

 changes in the temperature and the frequency of the measuring 

 current, and the phase of the current thru the condenser would 

 always be 90° ahead of that of the electromotive force impressed 

 on the condenser. In actual condensers these conditions are not 

 exactly fulfilled; the capacity decreases somewhat with increasing 

 frequency and the temperature coefficient of the capacity is 

 appreciable. Further, the phase of the current lags behind the 

 ideal position of 90° in advance of the electromotive force, by 

 an angle 9, which is usually small but always measurable. (In 

 what follows the angle 6 will be designated as the phase differ- 

 ence.) 



To account for these departures from the behavior of an ideal 

 condenser, all of which have their origin in the phenomenon of 

 electric absorption, a number of theories have been proposed 

 which give at least a qualitative explanation of the facts. Much 

 of the existing experimental data, has, however, been obtained 

 from experiments with a steady applied voltage, and with such 

 various times of charge and discharge, lengths of insulation or 

 short circuit, and such different galvanometer periods, as to ren- 

 der it very difficult, if not impossible, to decide whether or not 

 there is quantitative agreement between any given theory and the 

 observations. To meet this difficulty, measurements with alter- 

 nating currents would appear to be especially suitable to give 

 data for such comparisons, since the condenser is submitted to a 

 * perfectly definite cycle of charging and discharging. 



The present paper gives the results of measurements of the 

 capacity and phase difference of thirteen commercial condensers 

 by English, French, German and American firms at temperature 

 ranging from 10° to 35° in steps of 5°, and at frequencies of from 

 33 to 1000 cycles per second. In every condenser, the dielectric 



