STEADILY ALTERNATING CURRENT ON A LONG LINE. 329 



Finite Smooth Distortionless Line closed at Zero E.m.f. (Regu- 

 lar Transients). — If, instead of assuming an infinite line, or its 

 equivalent — a line of finite length AB, grounded at B through a re- 

 sistance equal to the surge resistance Sq — we apply the above stated 

 conditions to a finite smooth line, grounded at B through some other 

 impedance, reflected waves of voltage and current will return to the 

 generating end A, and will add themselves to the outgoing stream. 

 These successive increments build up regularly into the steady state, 

 at each and every point along the line.^ The initial outgoing e.m.f 

 and current are therefore transients in this case, as are also all the 

 reflected increments. Such wave transients may therefore be de- 

 scribed as " regular " wave transients, because their regular super- 

 position and combination bring about the final steady state. 



Finite Smooth Line, with Distortion, Closed at Zero E.m.f. 

 (Splash Transients). — If the uniform smooth line AB is not only 

 finite; but also has distortion, its surge impedance 2q will contain 

 reactance, and have some angle or slope. In the steadily alternat- 

 ing-current state, therefore, at any point along the line, the current 

 and voltage will not, in general, be in cophase. At an instant of 

 zero current, there will be some e.m.f. and at any instant of zero 



Fig. 2a. Fig. 2b. 



Illustrating formation of a Current Splash Transient. 



e.m.f. there will be some current. Consequently, if the switch is 

 closed at an instant of zero e.m.f., there will be some accompany- 

 ing " electric splash " ; because the current is then forced to start 

 from zero coincidently with the e.m.f. In Fig. 2a, the wave i of 

 2 Bibliography 6, and 13 page 79. 



