/•AV )/•./(,". 1 7 /r),V >iriR I'.tK.II.III. COM'I iTOIfS .Ml 



Wliiii ihc (HTmeabilily is unity, the solution, to the same order of 

 approximation as in the solid wire case, is 





(ifi) 



where 



V 2 />[« i(»o+fo)-ri(;<o-t'o)l-(/[«i(/<o -ru) +ri(Ho+t'o)l , , _, 



Pn = {-l}"2k's", H = l,2 . . . 00, 



■ - (2*)= 

 Since the resistance R„ of an isolated tubular conductor is given by 

 /?„_Real^--^^^ (19) 



equation (13) becomes equation (I) of the formulae in the next section. 

 This is the general solution for the case of non-magnetic conductors. 

 In general R may be calculated from this formula and tables of 

 Bessel functions. The ber, bei, ker and kei functions - and the recur- 

 rence fonnulae are sufficient to evaluate the Bessel functions but 

 the process is long. In the most important practical cases, the 

 conductors are rather large and the applied frequencies fairly high. 

 When this is true as well as when the tubes are very thin the formulae 

 usually involve only the limiting forms of the Bessel functions. These 

 s[H'cial results are gi\cn in the next section. 



III. .AlTERNATIM, ClRRENT RkSIST.WCE FoRMUI..\E FOR 

 XoN-M.\(..\KTir COVDITTORS 



The symlKils used are : 



a =outer radius of conductor in centimeters, 



a = inner radius of conductor in centimeters, v 



(" = interaxial separation between conductors in centimeters, 



k=a c 



X = conductivity of conductor in electroinagnetic c.g.s. units, 



- .\ convenient table of these functions for arguments from to 10 at intervals of 

 0.1 is incorporated in Mr. Dwight's paper ".\ Precise Mcthorl of Calculation of 

 Skin Kffect in Isolated Tulies," /. A. I. E. E., Aug., 1923. 



