216 POLYPHASE CURRENTS. [Exp. 



in a simple circuit, the hypotenuse of which is E, one side RI and 

 the other side XI; the principle is applied in the discussion of Fig. 10. 



38. Polygon or Mesh Method of Representation. As applied to 

 electromotive forces, there is in this method of representation a cer- 

 tain similarity between the diagram of connections and the diagram 

 for electromotive forces. It seems a natural method to apply in 

 many cases, as in Figs. 8, 9, 10. There is no essential difference 

 between it and the topographic method. Law (i), above, applies 

 directly and the electromotive forces around any mesh have a vector 

 sum of zero, introducing arrows with feather to tip in sequence. 

 (Compare analogy of network of highways, 31.) 



As applied to currents, the three currents drawn radially in Fig. 

 12 may be drawn as a closed polygon. So also in Fig. 7. Compare 

 likewise Fig. 14. 



39. Radial Method of Representation. In this method all vectors 

 for currents and electromotive forces are drawn radially from a 

 common center. This method is advocated by some for all cases 

 (Porter, Electric Journal, September, 1907), together with the double 

 subscript notation, in order that in involved problems ambiguity can 

 be minimized. For a star-connection the application is obvious. 

 For a delta-connection, we have the same radial diagram as for the 

 star-connection. See Fig. 12. 



A modified radial method, with vectors from several centers, is 

 illustrated in Figs. 14 and 15, and for particular cases, as in those 

 illustrated, possesses some advantages. 



40. Preferred Method. It is not proposed to advocate here a par- 

 ticular convention but rather to assist in making underlying principles 

 clear. One may choose or develop one method and apply it in all 

 cases; or he may select the method which is simplest or clearest for 

 each particular case. The important point is to see clearly the sig- 

 nificance of whatever method is used. 



