I'KOr.lC.tllOM ori:R I'AR.M.I.EI. VOMHK'TOHS 



where Rj, is the direct current resistance of the tliin tulmlar con- 

 ductor. K(is. (4t)) and (")()) a^;rce willi tlie corresponiliiin limits of 

 formulae V and VI respecti\el\ . 



The curves of the acconipain in^ ligiiri- iV^ not prilcnd in re|)risent 

 the proximity elTecl correction factor with precision. Thex' .ire, how- 

 ever, accurate for thin tubes, and inchcate the order of inaKnitu<fe 

 of the factor for \arious vahies of the thickness of the tubular con- 

 ductor and show the nature of its \ariation with respect to the applied 



r 



113 4 5 6 7 



10 II 12 13 14 15 16 17 18 19 20 



frequency. They are computed from formula (\') whicli is \alid 

 for quite high frequencies when the tubes are thin. When the thick- 

 ness of the tubes is greater, however, the range of validity with respect 

 to frequency is smaller, the dotted portions indicating a doubtful 

 degree of precision. It was previously pointed out in connection 

 with formula (I\') and is immediately deducible from physical con- 

 siderations, that all of the curves eventually coincide with the curve 

 for the solid wire which approaches the value 1.155 asymptotically. 

 As a simple application, suppose the resistance is required of a 

 tubular conductor with an outer radius of 0.4125 cm. (that of No. O 

 gauge A.W.Ci. copper wire) whose resistivity is 1090.5 electromagnetic 



