384 BELL SYSTEM TECHNICAL JOURNAL 



Umax = The value of // corresponding to Bmax, in oersteds. 



B, = The saturation value of flux density corresponding to an 



infinite magnetizing force. 



Br = Residual induction, the magnetic induction in a ring or 



infinitely long straight bar after the value of H has been 

 reduced from Hmax to 0. The value of B at the inter- 

 section of the hysteresis loop with the B axis, in gauss. 



He = Coercive force, the value of H required to reduce B from Br 



to O in a ring or infinitely long bar. The value of H at 

 the intersection of the hysteresis loop with the H axis, in 

 oersteds. 



Brem = Rcmaneuce, the magnetic induction at the magnetic 



equator of a permanent magnet with no external mag- 

 netizing or demagnetizing force. Values of Brem given 

 in this paper are without pole pieces on the magnets, in 

 gauss. 



L = The actual developed length of a magnet. 



A = The area of cross section of a magnet. 



D = The equivalent diameter of a magnet 



= 2VI/Vx 



L/D = The dimension ratio of a permanent magnet. 



{BH)max = The maximum value of the product of the coordinates of 

 the demagnetization curve for a given steel. The de- 

 magnetization curve is the portion of the hysteresis loop 

 between Br and He. 



T = Hardening temperature, absolute scale. 



To = Optimum hardening temperature, absolute scale. 



Factors that Determine the Remanence of a Permanent Magnet 

 Of the subjects enumerated in the introduction, the first is the one 

 that has been of greatest technical interest to the writer. During the 

 course of several laboratory investigations connected with shop prob- 

 lems, advantage was taken of the opportunity to secure data which 

 might be used for the purpose of making generalizations regarding rela- 

 tions among magnetic properties of magnet steels and permanent 

 magnets. 



The specific problem was to find out exactly the way in which the 

 remanence of a magnet is related to its shape and dimensions as well as 

 to the magnetic properties of the material of which it is made. Al- 

 though it requires the complete family of hysteresis loops for a given 

 piece of magnet steel to portray all of its various magnetic characteris- 

 tics, it was felt that possibly the combined influence upon the reman- 



I 



