CONTEMPORARY ADVANCES IN PHYSICS 



347 



Equation (9) gives the fieldstrength He which effects capsizal of a pair 

 of magnets initially transverse to the field, and having a clearance 

 {S — L) extremely small compared with their lengths L. For a 

 chain of magnets the value given for He would need only to be doubled ; 

 for any number of chains lying in the plane normal to the field, that 

 double value of He would remain valid. It is, we see, proportional 

 directly to M and inversely to the square of the clearance. 



Multiplying the expression given in (8) for sin Be by ML, we get the 

 component along the field-direction of the moment of any magnet 

 belonging to such a pair or to such a chain. If there were N magnets 

 grouped in pairs or chains in the plane normal to the applied field, the 

 magnetization / of the entire assemblage, parallel to the field-direction, 

 would be NAIL sin 6. The magnetization Ic at the verge of capsizal 



Fig. 11 — Initial curve and hysteresis loop of an Ewing model composed of 

 24 pivoted magnets. (After F. A. Ewing.) 



would be NML sin dc. The saturation-value of magnetization, /max, 

 would be NAIL. Thus we arrive at the equation for 7^: 



-' -'max 



S - L 

 LV2 ' 



(10) 



23 



