OX TRANSIENT ELECTRIC CURRENTS. 371 



Curve [I. for §■= 9.S 



„ III. ., „=10.5 (loaded 5 kg-.) 

 „ IV. „ „=: 9.8 (loaded 8 kg.) 

 For the wire of 0.43 mm. radius : — ■ 

 Curve V. for £-32.8 



,, VI. ., „= 9.!) (loaded 8 kg.) 



For wires under no longitudinal stress, the current increases 

 as the twist is increased. The rate of increase is at first very rapid, 

 hut the curves always show a Wendepunkt beyond which the 

 increase takes place only very slowly, up to the greatest amount of 

 twist applied in the present experiment. The current increases with 

 the twisting for all strengths of the magnetizing force, but in all cases 

 the increase of the current beyond a certain angle of twist takes place- 

 so slowly that the curve seems to be nearly parallel to the horizontal 

 axis. 



When the nickel wire is loaded, the effect of increasing the angle 

 of twist is somewhat different from what occurs under no longitu- 

 dinal stress. The current reaches the maximum value at a certain 

 angle of twist, and then begins to decrease as will be seen from curves 

 HI. and I\ . With wires 0.86 mm. thick, no such maximum was 

 not iced. 



The stress produced by twisting the nickel wire is a combina- 

 tion of compression and stretching as in the case of iron. The 

 magnetic susceptibility of nickel in the direction of contraction is 

 always decreasing as the twisl is increased, and that in the direction 

 of compression is always increasing - . Thus the component of circular 

 magnetization will be in the direction of compression. Moreover the 

 circular magnetization is always increasing- as the amount of twist 

 is made to increase. This increase, however, takes place very slowly 

 beyond a certain angle of twist, for when the stretching- and the 



