THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.] 



Art. XIII. — Circular Magnetization and Magnetic Per- 

 meability ; by John Trowbridge and E. P. Adams. 



Yery little quantitative work appears to have been done 

 upon the problem of the intensity of magnetization produced 

 by an oscillatory current in an iron wire. Previous work of 

 this kind has been done with oscillatory currents, either 

 of very much higher frequency or of very much lower 

 intensity than those used in the experiments about to be 

 described. 



In 1894, I. Klemencic* gave an account of some experi- 

 ments on this problem. He studied the effects of the oscil- 

 latory currents induced in an iron wire by Hertz waves, 

 reflected and received by parabolic mirrors. By comparing 

 the heat produced in a short iron wire through the action of 

 these oscillatory currents, with the heat produced in a similar 

 non-magnetic wire, he was able to arrive at a value for the 

 effective resistance of the iron wire to oscillatory currents. 

 Then by making use of Lord Rayleigh's formula : 



R' = Vi/^wR 



he calculated the value of the permeability of the iron. The 

 heat produced in each case was compared by the use of a 

 thermal junction held near the wire under investigation. In 

 this way he arrived at the value 118 for the permeability 

 of the iron to oscillatory currents, and estimated the maxi- 

 mum value of the field strength at 290. He reasoned that 

 since this very large maximum field strength produced such 

 feeble magnetization, the permeability of iron to oscillatory 



* Wiedemann's Annalen, liii, p. tOl. 



Am. Jour. Sci.— Fourth Series, Vol. XT, No. 63.— March, 1901. 

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