202 Mr. E. Y. Appletosi and Dr. B. van der Pol on 



the departure from the ordinary sinusoidal form. All the avail- 

 able theoretical discussions of this circuit do not lead one to 

 expect such marked differences in the current maxima. 



Fig-. 1, 



Triode 



L x = -L 2 = 0-1 henry : 



R ]= =B, 2 =20 ohms ; v ao = l20 Tolts ; v f =6 volts. 

 Oscillograms were taken with O 1 =0 , 5 mfd. and 1*0 mfd. 



The matter can be considered in further detail from a 

 consideration of fig. 1. If we assume that the resistances o£ 

 the coils Li and L 2 are small compared with the reactances 

 for the particular frequency considered, and tha.t the effec- 

 tive resistance of the vacuous space between grid and 

 filament is large, the relation between the induced anode 

 potential r a and the induced grid potential v g is given by 



_M 



where M is the mutual inductance between the coils L x and 

 L 2 . It is well known that M must be of negative sign to 

 produce self-excitation so that the anode and grid voltages 

 are 180 degrees out of phase. The value of the anode 

 current i a at any instant is a function of both the anode and 

 grid potentials, and the action of a triode is usuallv inter- 

 preted in terms of this characteristic relation 



which may be experimentally determined for static con- 

 ditions. 



It is also possible to determine experimentally the relation 

 between i a and v a when the values of v g are made consistent 



with the relation (v g = — t— rA mentioned above, i. e. 



