8 PRINCIPLES OF ELECTRICAL DESIGN 



to the practical engineer; but the present writer wishes to state, 

 most emphatically, that, in his opinion, the average engineer 

 does not rate imagination at its proper value, neither does he 

 cultivate it as he might, did he realize the advantages if only 

 from a grossly commercial standpoint that would thereby 

 accrue. There is to-day a tendency to underestimate the 

 value of abstract speculation and the pursuit of any study 

 or enterprise of which the immediate practical end is not obvious. 

 The fact that the indirect benefit to be derived therefrom may, 

 and generally does, greatly outweigh the apparent advantages 

 of so-called utilitarian lines of study, is generally overlooked. 

 It is an admitted fact that the outlook of the graduate from 

 many of the engineering schools is narrow: this is no doubt 

 largely due to faults in the system and the teachers; but the 

 student himself is apt to neglect his opportunities for the study 

 of subjects such as general literature, languages, history, and 

 political economy, on the plea that he would be wasting his time. 

 It is only at a later period of his engineering career that he 

 begins to realize how an intelligent and appreciative study of 

 these broader subjects would have stimulated his mind and 

 cultivated his imagination to a degree which would be a great 

 and lasting benefit to him in his profession. 



It is unfortunate that neither the nature of the subject nor the 

 manner in which it is presented in the following chapters is 

 likely to stimulate the imaginative faculty; but the writer be- 

 lieves that no apology is needed for referring in this chapter to 

 subjects outside the scope of the main portion of the book. 

 In presenting fundamental principles and showing how they may 

 be applied to the design of machines, it is necessary to arrange 

 the matter in accordance with some logical scheme; and it is 

 just because a book such as the present one cannot give, and 

 does not claim to give, all that goes to the making of a designing 

 engineer, that it was deemed advisable to say something of 

 a general nature relating to the art of designing electrical 

 machinery. 



The principles underlying the action of dynamo-electric 

 machinery may be studied under two main headings: 



1. The magnetic condition due to an electric current in a 

 conductor or exciting coil. 



2. The e.m.f. developed in a conductor due to changes in 

 the magnetic condition of the surrounding medium. 



