216 



PRINCIPLES OF ELECTRICAL DESIGN 



root, or narrowest part, of the tooth; and t in the formula is 

 therefore taken as 0.466 in. (item 34). The results of this 

 calculation are shown graphically in the upper dotted curve 

 of Fig. 81. 



2000 3000 4000 5000 6000 7000 8000 10000 

 Air Gap Density, B g , ( Gausses ) 



12000 14000 



Fia. 81. Curve giving relation between air gap and tooth densities. 



The " apparent" tooth density at the bottom of the tooth is, 

 by formula (63), 



Bt = 



1. 076 X 11 



which enables us to plot the lower dotted curve of Fig. 81. The 

 actual density in the iron of the teeth is almost exactly expressed, 

 for the low values, by formula (63) ; while at very high densities, 

 the actual tooth density approaches more and more nearly the 

 values calculated by formula (62) without ever quite reaching 

 them. It is therefore possible to draw a curve, such as the full 



