High-Frequency Induction- Coil. 'd'M 



In taking a series of observations the primary spark-gap is 

 at first disconnected, and ths current through the primary 

 circuit of the Rnhmkorff coil is adjusted by inserting resist- 

 ance or varying the excitation of the dynamo. Then the 

 terminal difference of potential of the primary condenser is 

 determined by the absolute electrometer and recorded. 



The next step is to connect in the primary spark-gap, 

 adjusting its length if necessary. Then starting the blower, 

 and allowing the spark to pass, readings are made of the 

 deflexions of the sensitive electrometer in the secondary 

 circuit and of both dynamometers. These readings are re- 

 peated several times, allowing the instruments to return to 

 zero after each reading ; and then the primary spark-gap 

 is again removed and the potential given by the Ruhmkorff 

 again noted, for a check. The great variations of potential 

 and frequency of the commercial circuit necessitated the use 

 of an independent generator of current. Table III. contains 

 part of the data thus taken. In column a is recorded the 

 primary spark-length in centimetres ; under V the potential 

 corresponding thereto ; under b the maximum potential 

 impressed upon the primary condenser when the spark-gap is 

 removed, computed on the assumption of a true sine-current. 

 The columns I b I 2 , V 2 give the observed effective currents in 

 both circuits, and potential in the secondary circuit, respec- 

 tively. Fig. 6. 



14 

 1-3 

 1-2 



© 



O.J.Q 



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25,000 



Volts. 



30,000 



The maximum impressed difference of potential, b, has been 

 used as the most available parameter for the intercomparison 

 of data, and is taken as abscissa in the accompanying plot 



