18 



CONSTANT-VOLTAGE TRANSMISSION 



hind it. Let R be the resistance of one conductor, rep- 

 resenting the loss of energy appearing as heat in the 

 conductors, and let X be the reactance of one conductor, 

 representing a drop in voltage caused by the alternating 

 magnetic field around the conductors. There will be a 

 drop along the conductors proportional to the current and 



QX 



FlG. 4. Vector Diagram of A. C. Line with Lagging 

 Current, Conditions Given at Receiver End. 



the resistance and reactance. The resistance drops, P R 

 and Q R are in phase with their respective currents, and 

 are drawn parallel to them. The reactance drops, P X 

 and Q X are drawn at right angles to the corresponding 

 currents. From the vector diagram, the supply voltage 

 E s may be seen to be given by the equation 



or approximately, 



or, to a rough approximation, 



The voltage drop is thus seen to be 

 PR + QX 



