DF.SIGX w/./A./( iihlSTlCS OF ELECTROMAGNETS 215 



ally of no pracUral valuo, and consiHiiii-nt!\-, \Try low pole fac-c den- 

 sities are generally rhoseii. 



As a result of the alx)ve considerations as well as the experience 

 gaineil in designing a great nutnher and ^■ariety of relays and electro- 

 magnets, the curves in Fiv;s. 1, 5, 6 and 7 have been drawn which show 



Fig. 7— Curves of Core Section and Pole Face Flux Density vs. Pull. These Cur%es 

 Assume That Between Loads of 1,000 and 10,000 Grams the Pole Face Area Will 

 be L'se<l Equal to the Core Section 



reasonable assumptions that may be made in working out new designs. 

 These curves are to be employed, of course, with due consideration 

 of the particular requirements in each case. 



From the af)ove discussion it is evident that magnetic irons which 

 are capable of high flux densities are particularly desirable for the 

 heavier magnets. The high densities permit of a small core section 

 and consequently a small and low cost magnet. The magnets which 

 control loads of a few grams, however, should be constructed of 



