STEADILY ALTERNATING CURRENT ON A LONG LINE. 351 



counterlockwise at the angular velocity of the impressed e.m.f. ; i.e., 

 60.6 revolutions per second. Its projection on the line OX at any 

 instant t seconds after arrival, will then give the instantaneous e.m.f. 



Fig. 17. Rotary Vector Diagram of e.m.f. at B during part of Transient 



Period. 



at B. When the vector OA has described 187°, and reached the 

 position OB' with an instantaneous value of Ob^ — 30.0 volts, 

 8.6 milliseconds later than the position OA, the second reflected 

 wave arrives. The resultant of OA and the second reflection has a 



