ELECTRIC OSCILLATIONS AND ELECTRIC WAVES. 229 



one complete cycle of electrical "movement" during the time 

 required for the wave to travel over twice the length of the line. 



(b) If the line is short-circuited at both ends, the wave is 

 reflected from one end with reversal of voltage, and again reflected 

 from the other end with reversal of voltage, and thus the wave is 

 brought back to its initial condition. Therefore the line passes 

 through one complete cycle of electrical movement during the 

 time required for the wave to travel over twice the length of the 

 line. 



(c) If the line is open at end A and short-circuited at end J5, 

 the wave is reflected from end A with reversal of current, then 

 reflected from end B with reversal of voltage, then reflected from 

 end A with reversal of current, and then reflected from end B 

 with reversal of voltage; and thus the wave is brought back to 

 its initial condition. Therefore the line passes through one 

 complete cycle of electrical movement during the time required 

 for the wave to travel over four times the length of the line. 



Fig. 163. 



The behavior of a transmission line as described in connection 

 with Figs. 153, 154 and 155 furnishes several good examples of 

 transmission line oscillation. Another interesting example is as 

 follows: Figure 163 shows a transmission line open at both ends, 

 cut apart in the middle, and connected to two batteries as shown. 

 One half of the line A A is thus charged so as to give a downward 

 electric field between the wires, and the other half BB is 

 charged so as to give an upward electric field between the wires 

 as shown by the fine vertical lines which represent the lines of 

 force of the electric field. When the two halves of the line A A 



