CHAFFEE. — IMPACT EXCITATION OF ELECTRIC OSCILL.A.TIONS. 281 



very close. In order to attain this the primary and secondary coils 

 ■were wound parallel on the same frame so that they interlocked. The 

 diameter of the coils is about 5 inches, and from one to seven or eight 

 turns were used. Direct coupling is almost as satisfactory as magnetic 

 coupling, but for regularity and freedom from harmonics the latter is 

 to be preferred, and was used throughout this experiment. The close- 



o 



> 



200 



100 



8 



4 



6 



la 



14 



16 



8 10 



OHMS 



Figure 8. Current Curves, with Changing Resistance. 



A = 100 meters. 

 lo = .55 ampere. 

 Ci= 175 X 10-5 m/. 

 C2=86 X 10-5^./. 



ness of the coupling, or, what is of more importance, the mutual 

 inductance between the primary and secondary circuits, should, for the 

 best results, be adjusted according to the amount of power delivered by 

 the secondary circuit. The connection between the mutual inductance 

 and the conditions in the secondary circuit is shown by the curves of 

 Figures 8, 9 and 10. 



In taking the curves of Figure 8, the primary supply current, the 

 primary capacity, and the secondary wave length were kept the same 

 in order to maintain constant the two syntony conditions, while a resist- 

 ance in the secondary circuit was varied for different numbers of turns 

 on the secondary helix. The primary capacity was 175 X 10"® /*./. ; 



