220 ADVANCED ELECTRICITY AND MAGNETISM. 



tages in the successive laps must always be equal to battery 

 voltage E, and of course there is always an odd number of 

 laps at B, one, or three, or five, etc. 



axis of I 



axi* of t 



axis of time 



Fig. 156. 

 Showing growth of current at B in 



Fig. 155 when R = -^. 

 3 \C 



Fig. 157. 

 Showing growth of current at 



Fig. 155 when R = - *& 

 5 \ C 



R in 



Note. Figures 153, 154 and 155 show what takes place when 

 a direct-current generator or battery is switched on to the line, 

 but on a line of moderate length a number of laps are formed in an 

 excessively short interval of time, and therefore Figs. 153, 154 and 

 155 show quite accurately what takes place immediately after an 

 alternator is switched on to the line, E being the value of the voltage 

 of the alternator at the instant of closing the switch. 



120. Transmission line surges which are produced when a 

 circuit breaker opens. When a circuit breaker opens, the arc 

 which is formed persists for a very long time, relatively speaking, 

 and the open gap in the circuit is filled with a fairly good conduct- 

 ing material which slowly loses its conductivity. It is about as 

 nearly impossible to produce characteristic line surges by opening 

 a circuit breaker as it would be to set up an abrupt water wave 

 in a canal by allowing a cubic mile of soft mud to flow into the 

 canal prism to stop a troublesome flow of water in the canal ; and 

 yet the moon, as a 60 cycle generator (60 cycles per month!), 



