(}<</~^- 



ALTERNATING CCKItKNT AND VOLTA< 



perpendiculars having corresponding numbers. A smooth curve 

 drawn through the intersections will be a sine wave. 



The si ne wave may also be plot ted from a table of sines. (Appen- 

 dix, page 458.) Mark a horizontal axis, Fig. 3 (a), in d L 



irh point erect an ordinate equal to the sine of the corre- 

 sponding angle. Thus at 30 the ordinate ab is 0.5; at 60 the 

 ordinate n/ is 0.866; at 90 it is 1.0; etc. The wave passes through 

 zero at 180, because the sine of 180 is zero. When the angle 

 becomes greater than 180, the sine becomes negative and the 

 falls lelow the line, as the sine is negative between 180 

 and 360. (See page 456.) The above is equivalent to plot- 

 ting the sines of the angle x, Fig. 1, x being the angle which 

 the plane of the rotating coil makes with the vertical at any 



:Mt. 



If the wave in question has a maximum value of B, Fig. 3 (6), 

 ;d of unity, the value of the ordinale at anv point may be 

 found by multiplying B into the sine of the corresponding angle. 

 Thai 



y = B sin x (1) 



Where ./ is in degrees. 



Example. Find the ordinates of a sine wave at points corresponding to 

 65 and 210, tho maximum ordinate being 40 units. Fig 3 (/>). 

 65 = 0.906. 



40 X 0.906 = 36.24. Ans. 

 Sin J10 = -(sin 210 - 180) = -sin 30 = -0.5. 



10 X (- 0.5) = - 20. Ans. } *' 



'i own in Fig. 3 (6). 



3. Cycle; Frequency. When the coil, Fig. 1. has 

 one revolution, it has pas 

 one p;iir of poles 'a north and a 

 nid it has traversed 



fc Thevoll Au.rB.no,, 



h.-i> trone through one ! \ / I 



eon, ,cle of values and 



the wave is now ready to 





ted " -AH"""'i <-'>. '- 



ne tbroimli <>ne coini oltage 



has g<ne tin' Lectrical ii!iie-<i<'grees. Tbei-et'oic, m 



