ELECTRIC OSCILLATIONS AND ELECTRIC WAVES. 231 



tribution as shown in Fig. 163 must be added to the sum of the 

 voltages in the several laps of the two ribbon waves, and to find 

 the current distribution over the line at any instant the currents 

 in the several laps of the ribbon waves must be added. 



wire wire , ^ 



wire wire 



+/ _ E _ 1 



. --- T. ------- a . 



=L 



+E +/ 



___ __ 



"* ~* i> 1 



______ ^E_ __ __ 1 ______ J 



12$. Moving wave trains. Before considering the type of 

 transmission line oscillation which is produced when an alternator 

 is connected across one end of a line it is necessary to discuss more 

 at length the type of wave train which is represented in Fig. 144. 

 When such a wave train travels along a transmission line the 

 voltage across the line at any point is a harmonic alternating 

 voltage and the current in the line at any point is a harmonic 

 alternating current of the same frequency, current and voltage 

 are in phase with each other (line resistance and line leakage 



Tf> j~r~ 



being negligible), and T = \ where E is the maximum 



value of the harmonic voltage, / is the maximum value of the 

 harmonic current, L is the inductance of the line per unit 

 length and C is the capacity of the line per unit length. 



Clock diagram models of moving wave trains.* The parallel 

 lines in the upper part of Fig. 169 represent a portion of a trans- 

 mission line; AB represents a long cylinder of wood with equi- 



* The student is supposed to be familiar with the use of the so-called clock 

 diagram in elementary alternating current theory. See Franklin and Esty's 

 Elements of Electrical Engineering, Vol. II, pages 52-65. 



