Electrical Resistance and Magnetic Permeability of Iron Wire at Radio Frequencies

Abstract

The magnetic permeability of iron wire at high frequencies.---G. R. Wait, investigating the magnetic permeability of iron and magnetite in high frequency magnetic fields, did not observe a critical variation of the permeability at about 3000 kilocycles (100 meters wave-length) as reported by Wwedensky and Theodortschik. It was suggested that the difference in the results might have been due to: (1) a difference in the kinds of iron investigated; (2) a difference in the strengths of the magnetic fields; and (3) a difference in the manner of suspending the iron sample. A sample of iron wire in which critical variations had been observed by Kartschagin and by Mitiaev was used in the present investigation with the same apparatus as had previously been used by Wait. Experiments were carried out in a magnetic field of an intensity equal to 0.5 gauss, as previously used by Wait, and also in a field of 0.01 gauss, the intensity of the field in which Wwedensky and Theodortschik observed the critical variation. Different methods of binding the sample were also tried. In no case was a critical variation in permeability observed.The electrical resistance of iron wire at high frequencies.---Mitiaev observed that the resistance of iron wire to a high-frequency current and its internal self-inductance underwent a critical variation at about 3000 kilocycles. Calculations of the permeability involving these quantities gave results in substantial agreement with those of Wwedensky and Theodortschik on the variation of permeability with frequency. The resistances of iron wires intermediate in size between those used by Mitiaev were measured by the resistance-variation method as described in Bureau of Standards Circular 74. The investigation was carried out between 4300 and 2500 kilocycles (70 and 120 meters wave-length). No critical change within the limits of observable accuracy was detected.