64 



TRANSMISSION LINE FORMULAS 



There will be an equal drop due to the flux produced by 

 the current in the wire B, so that the total drop due to 

 flux in air is 



- X io~ 9 



volts per centimeter of line, 



= 2ju X 741-1 logio- X io~ 6 (2) 



p 



volts per ampere per mile of single-phase line. 



Effect of Flux in the Conductor. Let i be the current 

 per unit area of section at any point in the wire shown in 



Fig. 14. (For the present 

 assume that i is the same at 

 all points of the section.) 



The total area of section of 

 the wire is xp 2 and therefore 

 the total current in the wire 

 is 



/ = iri 2 . 



Fig. 14. Section of Wire. 



The total current inside the 

 circle of radius x is 



/i = irix 2 . 



This is the only current forcing flux around the circular 

 path of width dx, since currents flowing nearer the surface 

 of the wire do not tend to produce magnetic lines in a 

 path which does not surround them. Thus the flux density 



at the radius x is 



2/1 2 irix 2 



10 x 



10 x 



2 irix 



10 



