194 



THE MAGNETIC CIRCUIT 



[ART. 60 



tors themselves are eccentric circles, with their centers on the 

 line .!/> extended. The equipotential surfaces are circular 

 cylinders, which are shown in Fig. 47 as circles passing through the 

 centers A and B of the conductors. Within the conductors them- 

 selves there are no equipotential surfaces. 



For purposes of analysis it is convenient to regard the field in 

 Fig. 47 as the result of the superposition of two simpler fields, simi- 

 lar to those of the concentric cable of the preceding article. Con- 



FIG. 47. The magnetic field produced by a single-phase transmission line. 



sider the conductor A, together with a concentric cylinder of an 

 infinitely large radius, as one conducting system. Let the current 

 flow through A toward the reader, and return through the infinite 

 cylinder. Let the conductor B with a similar concentric cylinder 

 form another independent system. The currents in the conduc- 

 tors A and B are to be the same as the actual currents flowing 

 through them, but each infinite cylinder is to serve as a return for 

 the corresponding conductor, as if there were no electrical connec- 

 tion between A and B. The currents in the two cylinders are 

 flowing in opposite directions and the cylinders themselves 



