﻿Mr. Rollo Appleyard on Dielectrics. 401 



The same sheet was then tested between hard metallic 

 plates, the results are indicated in Table IV. A. 



Table IV. a. 



l m 



2 m 



volts 

 150 



volts 

 300 



volts 

 450 



volts 

 600 



volts 

 750 



volts 

 900 



volts 

 1050 



volts 

 900 



186 

 189 



volts 

 750 



volts 

 600 



volts 

 450 



volts 

 300 



volts 



150 ; 



6 



235 

 237 



61-5 

 64-0 



161 

 171 



278 

 296 



156 

 162 



158 

 162 



127 

 129 



117-0 

 118-5 



950 

 965 



39-5 

 39-5 



115 





megohms 

 20,550 



10440 



6047 



3076 



870 



283 



135 



199 



549 



1641 



3915 



6212 



10720 



u 'Dielectric Hysteresis" 



" Dielectric hysteresis " is here alluded to in a sense which 

 needs a little explanation. The similarity in shape and 

 character between some of these curves and the well-known 

 forms of the hysteresis curves of magnetism is all that I wish 

 to imply, — it is not the phenomenon of" dielectric hysteresis " 

 proper. In an article in the Electrotechnische Zeitschrift, 

 29th April, 1892, p. 227, Steinmetz traces the analogy be- 

 tween a dielectric medium in an electrostatic field and 

 magnetic bodies in a magnetic field, with a view to deter- 

 mining whether the loss of energy in dielectrics, under the 

 influence of an alternating electrostatic field, would follow a 

 law similar to that which defines the magnetic losses due to 

 magnetic hysteresis. The experiments of Steinmetz, and 

 of Arno, have gone to show that the energy expended in a 

 dielectric medium, in an electrostatic field of alternating 

 potential, is sensibly proportional to the square-root of the 

 intensity of the electrostatic field. These losses are due to 

 " dielectric hysteresis w proper, and are quite distinct from 

 the mere change of resistance with voltage here described. 

 The experimental results of Steinmetz should, however, be 

 corrected for this other phenomenon of change, which, for 

 the time being, we may call " dielectric mutability/' or any 

 other term which denotes the variation of resistance with 

 voltage; for it is clear that the energy expended during a 

 cycle of potential cannot rightly be calculated upon the basis 

 of constant resistance assumed by Steinmetz. With this cor- 

 rection, if it could be determined and applied to his results, 

 the observed values, notwithstanding their present close 

 agreement with those calculated, may possibly be brought 

 even nearer to conformity. 



Phil. Mag. S. 5. Vol. 38. No. 233. Oct. 1894. 2 E 



