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XVI. The Change of Resistance of Nickel and Iron Wires 

 placed longitudinally in Strong Magnetic Fields. By 

 Edwin A. Owen, B.Sc, University Student, University 

 College of JSortli Wales, Bangor *. 



NUMEROUS experiments have been carried out on the 

 effect of magnetization on the resistance of ferro- 

 magnetic metals ; the most recent being those of Gray and 

 Jones t ? Barlow J, and W. E. Williams §. 



The experiments of Gray and Jones were carried out with 

 the object of determining simultaneous values in a specimen of 

 soft iron wire of the magnetizing force, the magnetization, 

 and the change of resistance due to magnetization. They 

 studied in particular the longitudinal effect, when the 

 direction of the electric current in the specimen is parallel 

 to the lines of magnetic force, and found that A<£ = al 4 

 represented approximately, in soft iron for fields ranging 

 from 30 C.G.s. to 250 c.G.s. units, the relation between the 

 magnetization 1 and the fractional increase of resistance Acf>, 

 i. <?., the increase of resistance divided by the resistance in 

 zero field. 



Barlow studied the same effect in nickel and found that 

 the change of resistance showed a decided maximum : — 



Ac/> = 0*0156, H = 2000 c.G.s. units, 



and in higher fields decreased continuously to the value 



Acj> -= 0-0100, H = 18,000 c.G.s. units. 



He suo-orested that this decrease was due to the end 

 elements of his coil, which were transversely magnetized. 

 The electrical resistance of nickel diminishes when trans- 

 versely magnetized in fields stronger than 2000 c.G.s. units, 

 and this may therefore explain the diminution in the value 

 of Acf> observed by Barlow in his experiments. 



The object of the experiments described in the present 

 paper was to examine the effect in still stronger fields, and 

 in doing so to employ specimens which were placed entirely 

 longitudinally in the field. For this purpose the specimens 

 examined took the form of very thin straight wires, only 

 about a millimetre long. These, while having sufficient 

 resistance to measure accurately, could be placed longitu- 

 dinally in the narrow gap between the pole-faces of an 

 electromagnet. 



* Communicated by Prof. E. Tavlor Jones, D.Sc. 



t Roy. Soc. Proc. 1900, vol. lxvii, p. 208, - 



t RoV Soc. Proc. 1902, vol, lxxi. p. 30. - ." ' . . 



§ Phil. Mag. October 1902, December 1903, Januarv 1905. 



