ALTERNATING CURRENTS 



THEIR THEORY, GENERATION, AND 

 TRANSFORMATION 



CHAPTER I 



1. Alternating currents. Frequency and wave-shape. Form factor and amplitude 

 factor 2. Simple sine waves. Vector diagrams 3. Relations connecting 

 amplitude, r.m.s., and arithmetic mean values of simple sine wave 4. Impressed 

 and induced e.m.f.'s. Self-inductance 6. Fundamental equation for a circuit 

 in which the current ia variable 6. Sine waves in circuits containing resistance, 

 self-inductance, and capacity 7. Power in alternating-current circuit. 



i. Alternating Currents. Frequency and Wave- 

 shape. Form Factor and Amplitude Factor 



AN alternating electric current is a current which periodically passes 

 through a definite cycle of 

 changes, the cycle consist- 

 ing of two half-cycles, 

 during one of which the 

 current is positive, and 

 during the other negative ; 

 the negative half-cycle 

 being, however, an exact 

 reproduction of the posi- 

 tive half-cycle, and the 

 only difference being one 

 of algebraic sign. 



The graph of an alter- 

 nating current would 

 therefore consist of a curve 

 such as that shown in 

 Fig. 1. We may speak of 

 the complete cycle of 

 changes as a complete 

 wave of current; and of 

 the two half-cycles as the 

 positive and negative half- 

 waves. 



Fio. 1. Graph of Alter- 

 nating Current. 



The time taken by the current to run through a complete cycle 



B 



