68 Dr. McLachlan on Effective Inductance, Effective 



of view. In Table IV. figures are given showing the ratio 

 of the first maximum and minimum values of the voltage 

 wave when the magneto is connected to a peak- voltage mea- 

 suring apparatus *. If we assume an oscillation of the 

 form e~ Kt sin cot, it is possible to calculate the loss due to 

 damping. Thus for the magneto used in these experiments 

 \=0'92 cojir, and the ratio of the actual peak voltage to- 

 that when A_ = is 1 : 1*5. The value of X depends of course 

 on the effective resistance and inductance under damped 

 oscillations. It is increased by increase of the former and 

 diminution of the latter. Hence X includes these two- 

 effects and is not merely a measure of the total energy loss 

 alone. The energy loss calculated from the above figures 

 is 3*6 x 10 -3 joule, a value which is of the same order of 

 magnitude as that obtained by method 1. 



It will be evident from the foregoing computations that 

 little advantage would have been gained by obtaining the 

 various coefficients of the circuits to a high degree of 

 accuracy. The above results amply demonstrate that in 

 its present form the magneto (at least the particular type 

 used in this research) is an inefficient apparatus for con- 

 verting electromagnetic energy into electrostatic energy of 

 high peak potential. The same conclusion was formulated 

 by Taylor-Jones using a rotating armature type magneto,, 

 who attacked the problem from a slight!}' different aspect. 



(10) Comparison of Loss ivith Armature in and out 

 of Housing. 



With the armature out of the housing we should expect 

 the loss prior to the passage of the spark to be a good deal 

 smaller than that which occurs in the housing when the 

 iron circuit is almost complete. Some approximate data 

 are given in Table IV. illustrating this point. 



m1 -, . .-, ,. 1st maximum of voltage wave 



The damping = the ratio -— ■ — -. „ ,— -^ . 



° 1st minimum or voltage wave 



The values of A are calculated from equation (10) using 

 the low-frequency inductances. 



It is of interest to observe that, using the same primary 

 condenser, the iron only increases the peak voltage about 

 threefold. The conversion efficiency, however, is trebled. 



* For method of measurement see MeLRclilan. Proc. Phvs. Soc. Feb. 

 1920. 



