ANALYSIS OF PULL AND MAGNKTlZATlON MKASlUK.MKX'l'S 



81 



4 8 12 16 20 



ABAMPERE TURNS, NI 



Fig. 1 — Magnetization curves. 



t)y A. C. Keller." In this case it is convenient to measure x at the center 

 line of the actuating card, whose location with respect to the axis of 

 rotation is indicated in Fig. 2. 



Apart from interpretation in terms of magnetic theory, any observed 

 point on a magnetization curve represents a measurement of the elec- 

 trical energy JJ stored in the coil, as given by the integral 



Jo 



ei dt, 



where e = d{Nip)/dt. It is represented by the area between the magneti- 

 zation curve and the axis of ^, and is given by: 



U 



f 



Jo 



NI dip. 



(1) 



This stored field energy may, in principle, be recovered in the decay 

 of the field, except for the portion lost l)y hysteresis in the matei'ial, 

 represented by the area between the increasing and decreasing mag- 



