ELECTRIC OSCILLATIONS AND ELECTRIC WAVES. 237 



in the two oppositely moving wave trains, and it is represented 

 therefore by a clock diagram arrow which is the vector sum of 

 the clock diagram arrows which represent the voltages at that 

 point in the respective moving trains. Now the vector sum of 

 arrows i and a in Fig. 173 is evidently zero, the vector sum of 

 arrows 2 and b in Fig. 173 is the arrow e2 in Fig. 172, the 

 vector sum of arrows 3 and c in Fig. 173 is the arrow 03 in 

 Fig. 172, and so on. 



Let us now consider the current distribution in the standing 

 wave train with the help of the current helices in Figs. 169 and 

 170. The vector sum of arrows No. I in Figs. 169 and 170 is the 

 arrow ii in Fig. 172, the vector sum of arrows No. 2 in Figs. 

 169 and 170 is the arrow i2 in Fig. 172, the vector sum of arrows 

 No. 3 in Figs. 169 and 170 is the arrow ^3 in Fig. 172, and so on. 



The actual distribution of current and the actual distribution 

 of voltage in a standing wave train on a transmission line is 

 shown in Fig. 174. This figure represents several vibration 

 segments in the middle portion of a long line. The upper 

 part of the figure A BA r B f represents the current distribution 

 in the wires at the instant when the voltage between the wires 

 is everywhere equal to zero, the flow of current at each point 

 in the line being represented by the short arrows and also by the 

 ordinate of the sine curve ii. This current rapidly charges 

 the wires (one wire positively and the other wire negatively) in 

 the regions 7V, and as the charges increase the current values 

 decrease. The ordinates of the successive curves ii, i2, ^3, 

 *4 and ^'5, represent the successive values of the current at each 

 point in the line, and the ordinates of the successive curves 

 eij e2, 03, e\ and 05, represent successive values of the voltage 

 across the line. The lower part of the figure, CD C'D 1 ', repre- 

 sents the distribution of electric field (voltage between the wires) 

 at the instant when the current is everywhere equal to zero. 



The sine curves ii, i2, -3, etc., and ei, e2, 03, etc., in Fig. 

 174 represent the successive current and voltage distributions 

 during one quarter of a cycle, that is, from the instant when 



