PREFACE 



This volume is intended for those who have such a knowledge 

 of direct currents as is given by Volume I. It presupposes no 

 knowledge of alternating currents. The first two chapters are 

 devoted to the development of the fundamental laws of alter- 

 nating currents and alternating-current circuits. Subsequent 

 chapters consider the application of these fundamental laws to 

 alternating-current measurements, to polyphase circuits, to 

 alternating-current machinery, and to power transmission. A 

 chapter on illumination and photometry has been included, as a 

 brief discussion of the underlying principles of light and of light 

 measurements is important in a general course in electrical 

 engineering. 



The development of the various alternating-current formulas 

 and of the operation of various types of machinery, transmission 

 lines, etc., are based on the fundamental laws of electricity and 

 magnetism as set forth in Volume I. Mathematical developments 

 are occasionally introduced, as supplementary to the descrip- 

 tive matter. As in Volume I, numerous illustrative problems 

 ami method- of making laboratory tests are given throughout the 

 text. 



This volume is intended to be elementary in character and 

 to act as a stepping stone to the more advanced texts of this 

 series. In many cases rigorous and detailed analysis is not 

 given, particularly in the chapter on alternat ing-current meas- 

 urements and in the liscii><ion of certain types of alteniating- 

 current apparatus. A thorough analysis of these subjects is 

 found in "Electrical Measurement s" l.y F. A. Laws, and "Prin- 

 ciples of Alternating Current Machinery" by R. R. Lawn- 

 both of which volumes arc included in t his series of Electrical 

 ring Texts. 



