Coefficient of Coupling of Oscillation Transformers. 7(51 



The instrument has also uses in the laboratory such as 

 determining capacities, inductances, and coefficients of 

 coupling of induction-coils. 



Fisr. 1. 



±n 



This circuit is given a form such that its inductance for 

 high frequency currents can be calculated. It is intended 

 to be used as follows : — Suppose we desire to determine the 

 capacity of a small leyden-jar for high frequency currents. 

 The jar is connected by outside and inside to one pair of ends 

 of the rectangle, and the other pair of ends are connected to 

 the secondary spark-balls of an induction-coil. We then 

 place the cymometer-bar near and parallel to one long side 

 of the rectangle, and set up oscillations in the leyden-jar 

 circuit with the induction-coil. Next, the cymometer 

 handle is moved until the vacuum-tube (preferably a Neon 

 tube) glows most brightly, and the value of the oscil- 

 lation constant read oft' on the scale. We then know that 

 this also must be the oscilliation constant of the jar circuit. 



The value of the high frequency inductance of the rect- 

 angular circuit is given with the instrument, and hence if 

 we call this value L x centimetres and the capacity of the jar 

 C, microfarads, and the scale-reading of the oscillation con- 

 stant of the cymometer corresponding therewith 1 , we have 



The calculated value of the inductance of the rectangular 

 circuit is obtained by the following formula. 



We consider in the first place two equal rectangular 

 circuits the sides of which arc respectively S and !S / in 

 length, placed with planes parallel and at a distance b 

 apart. If these circuits are filamentary circuits, then, starting 

 with the Neumann formula for the mutual potential energy 



