EFFECT OF TWIST ON TITE MAGNETIZATION OX NICKEL AND IRON. 201 



darin" - twisting. It will be afterwards shown that the curve is 

 analogous to that of iron subjected to large twists. 



Reversai of polarity for (liferent twists. — With regard to the rever- 

 sai of polarity for different amounts of twists, another set of experi- 

 ments was performed with a thin wire for a twist of ± 1°.7 per cm. 

 ( )n loading the wire with a weight of 5 kgs., the longitudinal stress was 

 sufficient to produce the reversal of polarity when placed in the field 

 = 0.34. The magnetization curve thus obtained is represented in 

 Fi"". 26. This curve is single looped, and has the same characteristic 

 as those obtained for the twist of ± 4°.o in weak magnetizing fields 

 under high tensions. The hysteresis in the present case is negative, and 

 is opposite to that for the twist of ± 0°.86. (Compare Fig. and 

 Fig. 26). The difference of hysteresis for these two twists must be 

 due to the difference of twist. To test this more fully, a new wire was 

 placed in the same condition as before with regard to 1 ho longitudinal 

 stress and the strength of the magnetizing field, and subjected to two 

 different twists of ± l°.2 and ± l.°4 respective! v. The curve obtained 

 from the former was similar to that for ± 0°.9, while the one given by 

 the latter agreed with that for ± I e . 7. Thus, for the above longitudi- 

 nal stress and ,§=0.34, the reversal of hysteresis must take place 

 between the twists of ± 1°.2 and ± 1 .4. Tins result indicates that 

 the hysteresis is influenced by the difference of twist although the 

 wire is subjected to high tensions. 



The next point to be examined is how the double looped curve 

 is transformed into a single loop when the opposite polarity is about 

 to appear. This interesting point was examined by increasing the 

 strength of the magnetizing force. For ft — 2.5 andr = ±l°.7, the 

 opposite magnetism is completely effaced, while at the same time the 

 curve (Fig. 27) becomes double looped. Although the loop formed 

 during positive twisting is very thin, it is quite certain that the 



