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XXXIII. Experiments on the High-Tension Magneto. — II. 

 By Norman Campbell, Sc.D* 



(Continued from p. 301.) 



11. A S was explained in the last paragraph of the first 

 jljL part of this paper, the object of the experiments 

 about to be described was to discover whether the relation 

 between the peak potential, the primary capacity, and the 

 coupling is in accordance with that predicted by the theory 

 of Prof. Taylor Jones. 



Plan of the Experiments. 



12. In most commercial magnetos the circuits are so 

 arranged that the coupling is as great as is consistent with 

 the mechanical limitations of the design ; any modifications 

 introduced must be in the direction of a reduction of the 

 coupling. Further, a little consideration will show that 

 the only method of reduction which would be possible in 

 practice, is that of. placing in series with the secondary 

 windings, which are coupled with the primary windings, 

 other secondary windings which are not so coupled ; if it 

 is desired during the change to keep the total secondary 

 self-inductance constant, the addition of uncoupled secondary 

 windings must he accompanied by a decrease of the windings 

 coupled with the primary. A reduction of the coupling by 

 adding uncoupled primary windings is impracticable, because 

 such a change would certainly decrease the primary current ; 

 while separation of the primary and secondary windings 

 (such as is easily possible in the induction-coil) is precluded, 

 unless the general design of the machine is completely 

 altered. 



The machine selected for investigation was of the "In- 

 ductor " type made by the British Thomson-Houston Co. 

 It has the advantage that the circuits are easily altered ; 

 since, moreover, it differs in important features from all 

 machines of the rotating armature type, experiments made 

 on it would give evidence of the generality of the con- 

 clusions already attained. The arrangement of the machine 

 is shown diagrammatically in fig. 7. The primary and 

 secondary circuits are wound on the portion a a' of the 

 laminated iron yoke A A. This yoke is fixed relatively to 

 the permanent magnet M and the frame of the machine. 



* Communicated by the Author. 



