1<)6 



BELL SYSTEM TECHNICAL JOURNAL 



Since the majjnetic coating is thin, and the "demagnetizing," or 

 "screening," effect of eddy currents small, it may be assumed that 

 // = 2//r. (It will not exceed that value, at least.) Using this 

 approximate value for //, the resistance increment due to hysteresis is 



Ri, = 8r?co/x-'/ 



a 



ab 



= 2r]fJ.O)BaL2, 



(8) 



0,8 



0.6 



Z 



UJ 



o 



< 



I- 

 o 



H 

 UJ 



I 



0.4 



Z 

 u 

 CC 



a. 



O 



0.2 I 



I- 

 < 



a: 



4 6 



FREQUENCY — KILOCYCLES 



Pig 3 — .Illustrating the fractions of the total current that are carried by the copper 



wire and by the magnetic sheath (19 gauge (B. & S.) wire with 



continuous loading of 25 millihenrys per mile). 



where Ba is the induction density at the outside boundary' of the 

 sheath. 



The Distribution of the Current in Wire and Sheath 



It is a matter of interest to know how much of the current is carried 

 by the magnetic sheath and hf)W the current is distributed over the 

 cross-section of the wire and sheath at various frequencies. The 



