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XX. 



THE CHANGE IN YOUNG'S MODULUS OF NICKEL WITH 

 MAGNETIC FIELDS. 



By WILLIAM BEOWN, B.Sc, 

 Professor of Applied Physics, Eoyal College of Science for Ireland, Dublin. 



[Read March 27. Published April 4, 1917.] 



Introduction. 

 In a very interesting paper by Honda and Terada 1 on "The Change of Elastic 

 Constants of Ferromagnetic Substances by Magnetisation," there are given, 

 along with other data, the results of experiments on the change of Young's 

 Modulus of elasticity in the case of nickel wires when under tensions varying 

 from 1-54 x 10 5 to 4-5 x 10 5 grammes per sq. cm., and when subjected to the 

 influence of direct longitudinal magnetic fields up to a maximum value of 

 400 c.g.s. units. 



As far as the present writer knows, no observations or measurements 

 have been made on the change of Young's Modulus in nickel wires when 

 they were subjected to the influence of alternating longitudinal magnetic 

 fields, or to direct and alternating transverse magnetic fields. 



The present paper, therefore, gives results obtained with longitudinal 

 alternating fields and with transverse fields direct and alternating, as well as 

 for longitudinal direct fields, for the sake of comparison of their effects on the 

 same wire. 



The constant longitudinal loads employed in the experiments were 10 5 

 and 2 x 10 5 grammes per sq. cm., which are smaller than the loads used by 

 previous experimenters ; and the working load, or the load which was put on 

 and off in determining Young's Modulus, was 2 kilos, or about - 45 x 10 5 

 grammes per sq. centimetre. 



The maximum magnetic field employed was 80 c.g.s. units, which was the 

 highest that could be safely applied without special cooling arrangements. 



On account of the great length of wire (226 cms.) used in the experiments, 

 a direct method of observation was employed, the measurements being made 

 by means of a microscope with a movable fine hair in the eye-piece. 



i Phil. Mag., Jan., 1907, p. 36. 



SCIENT. PROC. R.D.S., VOL. XV., NO. XX. 2 H 



