Title :
The Action of a High-Frequency Alternating Magnetic Field on Suspended Metallic Rings and Disks
Author_Institution :
Department of Physics, State Teachers College, Minot, North Dakota
fDate :
7/1/1934 12:00:00 AM
Abstract :
An experimental study of the torque on suspended nmetallic rings and solid disks caused by a high-frequency alternating magnetic field indicates (1) that G. W. Pierce´s expression for the torque on a ring is valid over a wide range of frequencies, and (2) that, as a function of frequency, intensity of field, thickness, and conductivity, the torque on a disk is sufficiently similar to that for a ring to suggest that it varies as τp2Hv2/R(1+τ2p2) in which τ is the time constant of the disk, R, its effective resistance, and p is 2π times the frequency of the applied magnetic field whose virtual intensity is Hv. Measurement of this torque on a ring or disk apparently constitutes a convenient and practicable method of measuring the intensity of a high-frequency magnetic field. Comparative measurements on a ring and disk indicate that the greater part of the induced circular current in a disk at high frequencies flows near its periphery, primarily because of the shielding action of the peripheral currents, a result in agreement with experimtents made previously by Zenneck. A reproducible depression in the torque-frequency curve of a thin silver disk was observed at 700 kilocycles.
Keywords :
Conductivity; Current measurement; Electrical resistance measurement; Frequency; Magnetic field measurement; Magnetic fields; Magnetic levitation; Magnetic shielding; Solids; Torque measurement;
Journal_Title :
Radio Engineers, Proceedings of the Institute of
DOI :
10.1109/JRPROC.1934.226740