PRINCIPLES OP ALTERNATING CURRENT 



201 



Form Factor. It is sometimes desirable to know the 

 ratio of the virtual value of a wave to its average value. The 

 ratio is called the form factor of the wave. 



The average value of a simple sine wave may be obtained 

 by measuring the area between the curve and the X axis 



Flat to 



Form fact 



or=1.00 



Peaked wave 

 rm factor=Kl6 



FIG. 120. Extreme Cases of Wave Distortion. Actual waves are 

 not as bad as these. 



and then dividing this area by the base of the curve. The 

 average value of a sine wave is found to be equal to 



E m X- or .636# m . 



Hence the form factor is equal to 



For a wave more peaked than a sine wave the form factor 

 is greater than 1.11 and for a flat topped wave it is less than 

 this value. Two extreme cases are given in Fig. 120. 



46. Vector Representation. It is inconvenient to always 

 use the curve diagram for representing currents and e.m.fs.; 

 a much simpler method is by means of the vector diagram. 



