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VIIT. 



THE CHANGE IN THE EIGIDITY OF NICKEL WIRE WITH 

 MAGNETIC FIELDS. 



By WILLIAM BROWN, B.Sc, 

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



AND 



PATPJCK O'CALLAGHAN, A.E.C.Sc.L, A.I.C., 



Demonstrator of Physics in the same College. 



Read June 22. Published August 9, 1920. 



In March, 1917, one of us brought before this Society the results of some 

 experiments on " The Change in Young's Modulus of Nickel with Magnetic 

 Fields."' The present communication is a continuation of that work, and 

 gives the results of some experiments on the change in the rigidity of nickel 

 wires when subjected to the influence of magnetic fields, both longitudinal 

 and transverse. 



The change in the rigidity of nickel due to direct longitudinal magnetic 

 fields, and under various loads, has been done by Honda and Terada;* but, 

 as far as the present writers know, there have been no observations or 

 measurements made on the effects of alternating longitudinal magnetic 

 fields, or of direct and alternating transverse fields, and the present paper 

 gives the results of some work with these types of magnetic fields. 



The nickel wire used in the experiments was about 65 ems. long, 

 1-685 m.iu. diameter, and of simple rigidity, 810 x 10" grammes per 

 square cm. 



A statical method of measurement was adopted, where the wire was 

 arranged in a horizontal position, and firmly fixed at one end. On the other 

 end there was fixed a light three-jaw clutch, which also supported a small 

 light plane mirror, with its reflecting surface in the plane of the axis of the 

 wire under test. On the end of this clutch there was a hook, to which was 

 attached one end of a string of tortionless floss silk, the other end of this 

 string being passed over a pulley, and attached to a scale-pan which carried 

 the loads applied to the wire. The end of the nickel wire at the small 

 clutch was supported on a horizontal piece of glass tubing, 2 m.m. in diameter, 



1 gcient. Proc. R.D.S., vol. xv, No. 20. ~ Phil- Mag., January, 1907, p. 36. 



