

0. Barus — Apparent Hysteresis. 



105 



Table 



I. — Magnetostriction of soft iron in 



longitudinal fields. 



Current 













Field. 



Twist. 



Slope a. 



Slope 1). 



Cycle slope. 



Displacement. 



2 amp. 



+ 90° 



+ 0*5 



+ 6'0 



+ 3'0 



+ 5-5 



200 













4 amp. 



+ 45 



— 3-0 



+ 6-0 



+ 1-5 



+ 4-5 



400 



90 



— 1-0 



5 5 



3'0 



6-0 





180 



+ 1-0 



5-0 



3-0 



7'5 





360 



+ 2-0 



3-5 



2-5 



5-0 



4 amp. 



45 



— 2-0 



6-0 



2-0 



4-0 



400 



90 



— 1-0 



6-0 



2-5 



7-0 



4-0 



8 amp. 



+ 45 



— 2-0 



+ 6'0 



2-0 



4-0 



800 



90 



— 0-5 



6'5 



3'0 



7'0 





180 



+ 2-0 



5-5 



4-0 



6-0 





360 



+ 3'0 



4-0 



3'5 



4-0 



Length, 35 ( 



m . Diam 



., '024 cm . 



Deflections in scale 



parts (-001 



radian or -057°) per 90° of twist of each wire. 



M^r-l 



Hence with increasing twist the temporary deflection a and 

 the permanent deflection h make respectively from large nega- 

 tive and from large positive values toward the same interme- 

 diate positive limit, which is larger for the larger field. The 

 slopes of the cycles pass from small values rapidly into con- 

 stant values as twist increases but they probably also pass 

 through maxima as above. Finally the displacement of the 

 zero for increasing twist marches through a definite maximum 

 located at small angles of twist when the field is greater. 



8. To obtain further relevant data it will next be necessary 

 to twist between three angles, the middle one being zero and 



