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XIV. 



THE SUBSIDENCE OF TORSIONAL OSCILLATIONS IN 

 NICKEL WIRES WHEN SUBJECTED TO THE INFLUENCE 

 OF ALTERNATING MAGNETIC FIELDS. 



By W. BROWN, B.Sc, 

 Professor of Applied Physics, Royal College of Science for Ireland, Dublin, 



J. SMITH, M.A., 

 Research Student in the College. 



[Read Januauy 27. Published Febbuary 20, 1914.] 



About three years ago, one of us brought before this Society the results of 

 some experiments on the subsidence of torsional oscillations in iron and 

 nickel wires, wlien they were subjected to the influence of longitudinal 

 magnetic fields, the magnetic fields being produced by continuous direct 

 currents.' These results, among other things, showed a marked increase in 

 the damping of the torsional oscillations in magnetic fields up to a certain 

 value, depending on the longitudinal load on the wire, and for higher 

 magnetic fields a remarkable decrease in the damping of the oscillations. 



Tiie present communication gives results obtained with nickel wires when 

 they were subjected to the influence of alternating magnetic fields of different 

 frequencies, and for comparison, each set of experiments, with the alternating 

 magnetic fields, was preceded by an experiment with a direct longitudinal 

 magnetic field of the same value, and also one in which the wire was under 

 the influence of the vertical component of the Earth's magnetic field, about 

 0'45 e.g.s. units. Tlie results of this latter have, however, only been recorded 

 once iu this paper, and that in the form of a curve in the figure (p. 221). 



Drago" has shown that the rapidity of the damping of torsional oscil- 

 lations in an iroji wire diminishes under the influence of electrical oscillatory 

 discharges and alternating currents. The wire he used was 20 cms. long and 



' Scient. Proc. Roy. Dub. Soc, vol. xiii (N.S.), No. 3, p. 32. 

 * Nuovo Cimento, seiie vi, vol. iii. 



SCIENT. PROC. E.D.S., VOL. XIV., NO. XIV. 2 K 



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