File:The Measurement of Magnetic Hysteresis (1902) (14592145528).jpg

Identifier: philtrans05780600 (find matches)
Title: The Measurement of Magnetic Hysteresis
Year: 1902 (1900s)
Authors: Searle, G. Bedford, T.
Subjects: Proceedings of the Royal Society of London Philosophical Transactions of the Royal Society
Publisher: Royal Society of London

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ns. The values of B^ and W were determined immediately afterthe wire broke, the tests showing that, when the stress was relieved by the fracture,both Bq and W fell to about half the values they had just before the fracture. ThusBo fell from 2950 to 1510, while W fell from 2410 to 1044. We found that when the wire had been twisted W diminished considerably withcontinued reversals, even after 20 cycles of magnetisation. § 61. ExperimeUts on Soft Iron Wire (2); Hq = 5-0.—-The second specimen (2) wastreated rather differently. The wheel was turned through a definite number of ON THE MEASUEEMENT OF MAGNETIC HYSTEEESIS. 83 revolutions, measured from its position when the wire was initially free from torsionthe number being read on the counter. The wheel was then clamped in thisposition, and, after 20 cycles of magnetisation, observations were made for Bq andW. The wheel was now undamped, and the wire was allowed to untwist so as to rid 8000 8000 if 7000 8000Scaia for W I Scaie for Bo7000
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9000 6000 5000 4000 J 3000 000 1000 0 10 20 30 40 50 GO 70 80 90 TOO 100 80 80 70 60 50 40 ,30 20 10 0 Fig. 12. itself of torsional stress ; after twenty more cycles of magnetisation, the new valuesof Bq and W were then determined for this condition of the wire. The wheel wasthen turned still further, and fresh observatious were made, the process beingrepeated until the wire broke. The results are shown in fig. 12. The curves for Bqand W when the wire was under torsional stress are marked (2a), and those for zerostress are marked (26). For the sake of clearness, the origin for these four curves isat the right side of the diagram. The wire in untwisting turned the wheel back through an angle depending uponthe twist fromx which it was endeavouring to rid itself—an angle which increased withthat twist. After a twist of one revolution the wire turned the wheel back through100^, retaining a permanent set of 260, while, after a twist of 100 revolutions,the wheel was turned back through 29

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