ALTERNATING CURRENT AND VOLTAGE 3 



2. Sine Wavers. It was shown in Vol. I, Chap. X, that when 



-ingle coil 'rotates at constant speed in a uniform field, Fig. 1, 



tin alternating emf. is generated. This emf. is zero when the 



plane of the coil is perpendicular to the field, and reaches its 



maximum value when the plane of the coil is parallel to the field. 



(See Vol. I. puirr 21H. Fig. 188.) The successive values of the 



emf. may be represented by a smooth curve called a sine wave 



for the reason that the values of the emf. are proportional to the 



Emf. Wave 



Decrees 



of :ui :iltrrn:itiMK emf. 



sine of the aniile ./ which the coil makes with the vertical, Fig. 1. 

 This will be discussed more in detail later. 



For various reasons, commercial generators do not give exact 



sine waves of emf. In fact, the emfs. of some generators ditYer 

 lally from a sine Mill, most commercial genera- 



tiave travel <>f emf. which are sufficiently close to a sine 



warrant their he inn I rented as such. 



not a sine wave, it may he resolved into a 061166 

 of fundamental and higher frequencies. Each one 

 of the>e component- may then In- dealt with as a sin- 

 Tin ordinarily encountered in practice are app 

 match Bine ':d may he treated l>y simple ON 



