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BELL SYSTEM TECHNICAL JOURNAL 



constitutes a sufficiently convincing verification of the correctness of 

 Evershed's criterion. 



The chief objection to the use of Evershed's criterion is that a 

 number of points on the demagnetization curve for a piece of magnet 

 steel must be known before the numerical value of the product {BH)max 

 can be determined. The quantity Br He is more easily obtained than 



10,000 



8000 



6000 



I 4000 



I 



I 2000 







I 



10,000 

 8000 

 6000 

 4000 

 2000 

 



6000 



4000 



2000 







BH X 10-6 

 Q 25 0.5 0.75 1.0 



BH X 10-6 

 0.25 0.5 0.75 1.0 1.25 



200 100 



H IN OERSTEDS 



2 4 6 8 10 



LENGTH OF BAR 

 IN INCHES 



12 200 100 



H IN OERSTEDS 



2 4 6 8 10 12 



LENGTH OF BAR 

 IN INCHES 



Fig. 10 — -Curves showing experimental verification of validity of Evershed's criterion 

 for magnetic quality of permanent magnet steels. 



{BH)max but its validity as a criterion cannot be established ij:om 

 theoretical considerations. Accordingly, the values of {BH)max and 

 Br He were determined by actual measurement for a large number 

 of bars of different kinds of magnet steel. In Fig. 11 are shown 

 the values of Br He plotted against the corresponding values of {BH)max- 



