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BELL SYSTEM TECHNICAL JOURNAL 



and its "vector diagram" (Fig. 3) both show that, in the hmiting case 

 of a perfectly conducting wire {Rh = 0), Vn and Uh would exactly 

 balance each other, their values being exactly equal and opposite; 



Uh = 

 "CURRENT 

 VOLTAGE " 



Fig. 3 — Vector diagram relating to wire H of Fig. 2. 



and that, in the case of an actual wire of low resistance, Vh and Uu 

 nearly balance each other, their values being nearly equal and nearly 

 opposite, so that their resultant Wh = RhIh is a small residual voltage, 

 although Vh and Uu individually may be very large compared with 

 Wh. 



The Mutual and Self Impedances 



The mutual impedance (and similarly the inductive part of each 

 self impedance) of the wires A and B (Fig. 1) cannot be defined as the 

 negative of the voltage induced in either by unit current in the other, 

 because the induced voltage necessarily has unequal values along the 

 various filaments of which the disturbed wire may be regarded as 

 composed. Thus in general this definition, which might be called the 

 elementary definition, is applicable only to the individual filaments 



