INDUCTANCE AND CAPACITY 



425 



fifth harmonics. As in all electrical resonators, the ohmic resis- 

 tance of these coils must be kept low if the resonant point is to 

 be sharply defined. 



The relation between the inductance and capacity necessary 

 to resonate a harmonic of frequency / is given by 



or if C be in microfarads and L in millihenrys, 



_ 5,033 



= 



n& 



Li 



r 3 ! /TQisffih I 



L- feM ywJ 



Cr.l-=>J Adjustable 



Adjustable Inductance 



Condenser and Air Core 



Transformer 



Adjustable 

 Condenser 



Bridge 



Second ^2 

 Adjustable 

 Inductance and 

 Air Core Tr.anslo.rmer 



FIG. 249. Diagram for Fleming and Dyke resonator. 



The capacities and inductances used by Fleming and Dyke were 

 as follows: 



To obtain a pure sine wave it was found necessary to use a second 

 resonator electromagnetically coupled with the first by an air- 

 core transformer formed by thrusting a secondary coil wound 

 on a paper tube, T\, into the first adjustable inductance, L\. The 

 capacities used in this second resonator circuit could be varied 

 from 0.25 to 8.25 microfarads. As indicated, the bridge cur- 

 rent is derived from a second air-core transformer, its secondary, 

 TZ, being inserted in L 2 . 



DEVICES FOR MAINTAINING CONSTANT SPEED 

 In many methods of measurement, particularly when dealing 

 with inductances and capacities, it is necessary accurately to 



