46 Dr. Mckachlan on Effective .Inductance, Effective 



the iron core than with it*, the value o£ B/ in expression (8) 

 was not negligible. By increasing C and keeping w constant, 

 there was no measurable difference with and without the iron, 

 whether the latter was very thick or very thin. Thus the 

 reduction in current is in this case brought about by dielectric 

 and copper loss. The dielectric loss can be represented in 

 the usual manner by a high resistance in parallel with the 

 condenser. This is equivalent to a series resistance of small 

 magnitude. Since the current passing through the inductance 

 (fig. 5) is extremely small, it can be neglected. The conditions 

 that -13 



a> 2 2 (R 2 2 + a> 2 L 2 2 ) 



is negligible, and that co 2 L 2 C is much greater than unity, 

 must be observed. Under these conditions the coil with the 

 condenser in parallel is, therefore, equivalent to the circuit 

 of fig. 7. 



Fig. 7. — Representation of secondary winding as a condenser shunted 

 by a high resistance, when certain conditions (specified in text) 

 are fulfilled. 



WWWVMj 



When &) 2 (>'R/ is large compared with unity, the arrange- 

 ment of fig. 7 is equivalent to a condenser C in series with a 

 resistance of magnitude 



1 



li 



[see fig. 8). 



- o) 2 C 2 R, 



where ~R d represents the resistance of the dielectric to alter- 

 nating currents under the special conditions in the magneto 



Fig. 8. — Circuit equivalent to that of fig. 7. 

 c 



*> 2 C 2 Rd. 



—mm — i 



* By calculation and measurement, L 2 without the iron w: 

 order of 3 henries for the coil used in these experiments. 



the 



