Resistance, and Self- Capacity of Magneto Windings. 45 

 I£ &) 2 L2C is large compared with unity, we get 



z = R 2 _ ;o)C(R 2 2 + 6 ) 2 L 2 2 ) 



o) 2 C 2 (R 2 2 + a> 2 L 2 2 ) a) 2 C\R 2 2 + a) 2 L 2 2 ) 



+ ^t. = »'+At5 • • (8) 



o) 2 2 (R 2 2 +a)2L 2 2 ) ' j/VC " ' ><J 



t. <?.,, the combination is equivalent to the condenser C in 

 series with a non-inductive resistance 



g) 2 C 2 (R 2 2 + g> 2 L 2 2 )' 

 as shown in fie\ 6. 



Fig. 6. — Circuit which behaves in the same manner as that of fig. 5 t 

 when certain conditions (stated in text) are fulfilled. 



— \wmn 



This is due to the fact that by far the greater portion of the 

 current passes into the coil as displacement current and not 

 as a circulating current passing through the coil. In order 

 to obtain this condition, it is essential that &> 2 L 2 (J should be 

 large compared with unity. Since C must be small so that 

 a small difference in C* affects the tuning of the circuit, 

 a) 2 and therefore/ mast be correspondingly large. 



In carrying out experiments using the above method, 

 it was found that the resonance currents were different 

 according as the magneto or a condenser of equal capacity 

 was connected in circuit. It was greater in the latter 

 case. This difference must be due to either copper, iron,, 

 or dielectric loss, or all of them. In order to investigate 

 this point, the resonance currents were measured (a) with 

 the armature in the housing, (b) with the armature out 

 of the housing, (1) with the iron core in place, (2) with the 

 iron core withdrawn. The current was smaller in case (a) 

 than in case (b). In the latter case it was greater with the 

 iron than without it. The frequency was so high that 

 a> 2 C 2 E 2 2 + ft) 2 L 2 2 ) v\as much greater than R 2 except when 

 the iron was removed. Thus, since L 2 is much less without 



* If the capacity in parallel with the coil is large compared with the 

 self-capacity, the distribution of current in the coil will be fairlj 

 uniform. 



