A CONDUCTING SPHERE IN A TIME VARYING MAGNETIC FIELD

Geophysics ◽  
1951 ◽  
Vol 16 (4) ◽  
pp. 666-672 ◽  
Author(s):  
James R. Wait
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Eddy Currents ◽  
Transient Behavior ◽  
Step Function ◽  
Conducting Medium ◽  
Time Varying ◽  
Geophysical Prospecting ◽  
Conducting Sphere

The secondary magnetic fields are evaluated for the case of a conducting sphere in a relatively poorly conducting medium under the influence of a time varying magnetic field. The sinusoidal and step function responses are both considered. The responses so calculated are thought to be useful in a geophysical prospecting method which utilizes the transient behavior of induced eddy currents in a highly conducting ore zone.

INHOMOGENEOUS CYLINDRICAL ORE BODY IN PRESENCE OF A TIME VARYING MAGNETIC FIELD

Geophysics ◽  
1962 ◽  
Vol 27 (3) ◽  
pp. 386-392 ◽  
Author(s):  
Janardan G. Negi
Keyword(s):  
Magnetic Field ◽  
Magnetic Permeability ◽  
Propagation Constant ◽  
Homogeneous Medium ◽  
Step Function ◽  
Practical Case ◽  
Time Varying ◽  
Geophysical Prospecting ◽  
The Core ◽  
Ore Body

The secondary fields are evaluated for the case of an inhomogeneous conducting cylinder embedded in an infinite homogeneous medium under the influence of a time varying magnetic field. Both sinusoidal and step function responses are studied in detail for a practical case of interest in geophysical prospecting in which the exterior medium is relatively poorly conducting, the propagation constant in the cylinder is varying linearly across the section of the core, and the magnetic permeability is the same everywhere.

scholarly journals EM Site A.C. Magnetic Field Sources, Surveys and Solutions Part IV: Survey Data Analysis

1996 ◽  
Vol 4 (4) ◽  
pp. 20-21
Author(s):  
Curt Dunnam
Keyword(s):  
Magnetic Field ◽  
Data Analysis ◽  
Magnetic Fields ◽  
Survey Data ◽  
Field Survey ◽  
Survey Methods ◽  
Time Varying ◽  
Measured Field ◽  
The Magnetic Field ◽  
Analyze Data

Up to the present waypoint in this series on EM site magnetic fields, we have identified typical sources of time-varying magnetic field intensities, examined salient field characteristics and illustrated correct survey methods. Our goal this month is to analyze data collected at a proposed site and answer the key question of whether or not the candidate site is, as far as magnetic fields go, acceptable for EM use. In the process of analyzing the magnetic field survey data we will define some of the interpretive techniques involved and observe the distinction between localized (a.c. power) and non-localized (geomagnetic) time-varying fields. Finally, we will discuss the implications of EM susceptibility threshold vs. measured field ratios when considering remedial site shielding.

scholarly journals The loss of energy in metal plates of finite thickness, due to eddy currents produced by alternating magnetic fields

1926 ◽  
Vol 111 (759) ◽  
pp. 604-614 ◽  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Eddy Currents ◽  
Finite Thickness ◽  
Metal Plate ◽  
The Self ◽  
Alternating Magnetic Field ◽  
Metal Plates ◽  
Alternating Magnetic Fields

The induction of eddy currents in metal plates which are subjected to alternating magnetic fields has been discussed by Clerk-Maxwell, J. J. Thomson and many others. When an alternating magnetic field is produced normal to the surface of a metal plate, eddy currents are induced at the surface of the plate, which gradually penetrate its interior, the current dying away as it penetrates more deeply into the metal. The diffusion of the currents into the plate depends upon the self-induction and resistance of the paths along which they flow, and can be calculated by the same kind of formula as is used for determining the conduction of heat through a metal slab.

scholarly journals The Steady Currents Driven in a Conducting Sphere Placed in a Rotating Magnetic Field

1984 ◽  
Vol 37 (5) ◽  
pp. 521 ◽  
Author(s):  
WN Hugrass ◽  
HA Kirolous
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Equatorial Plane ◽  
Rotating Magnetic Field ◽  
Toroidal Magnetic Field ◽  
Weakly Nonlinear ◽  
Conducting Sphere

The steady currents (and the associated steady magnetic fields) generated in a conducting sphere placed in a rotating magnetic field are calculated in the weakly nonlinear limit. It is found that the steady driven current has a poloidal and a toroidal component. The steady toroidal magnetic field associated with the driven poloidal current has opposite senses above and below the equatorial plane; the net toroidal flux is zero. The relevance of this result to some recent observations in the Rotamak experiment is discussed.

Transient magnetic field formulation for solid source conductors

2020 ◽  
Vol 64 (1-4) ◽  
pp. 1539-1545
Author(s):  
Georg Wimmer ◽  
Sebastian Lange
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Vector Potential ◽  
Numerical Scheme ◽  
Eddy Currents ◽  
Magnetic Vector Potential ◽  
Magnetic Vector ◽  
Time Step ◽  
Azimuthal Component ◽  
Transient Magnetic Fields

The formulation for the azimuthal component of the magnetic vector potential for axisymmetric magnetostatic applications is well known. However for transient magnetic fields with solid source conductors and eddy currents the formulation has to be revised. A variable transformation is introduced to remove the singularity from the numerical scheme. The numerical error cannot accumulate and is put instead to the postprocessing at every time step.

Time-varying magnetic fields increase cytosolic free Ca2+ in HL-60 cells

1990 ◽  
Vol 259 (4) ◽  
pp. C687-C692 ◽  
Author(s):  
J. J. Carson ◽  
F. S. Prato ◽  
D. J. Drost ◽  
L. D. Diesbourg ◽  
S. J. Dixon
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Electromagnetic Fields ◽  
Biological Effects ◽  
Static Field ◽  
Free Calcium ◽  
Time Varying ◽  
Parallel Control ◽  
Magnetic Resonance Imaging Mri ◽  
Radiofrequency Electromagnetic Field

Electromagnetic fields have been reported to cause a variety of biological effects. It has been hypothesized that many of these phenomena are mediated by a primary effect on the concentration of cytosolic free calcium ([Ca2+]i). We investigated the effects of exposure to electromagnetic fields on [Ca2+]i in HL-60 cells using the Ca2(+)-sensitive fluorescent indicator indo-1. Indo-1-loaded cell samples were exposed to a radiofrequency electromagnetic field, a static magnetic field, and a time-varying magnetic field, which were generated by a magnetic resonance imaging (MRI) unit. We found that a 23-min exposure to all three fields, in combination, induced a significant increase in [Ca2+]i of 31 +/- 8 (SE) nM (P less than 0.01, n = 13) from a basal level of 121 +/- 8 nM. Also, cells exposed to only the time-varying magnetic field had a mean [Ca2+]i that was 34 +/- 10 nM (P less than 0.01, n = 11) higher than parallel control samples. Separate exposure to the radio-frequency (6.25 MHz) or static field (0.15 T) had no detectable effects. These results demonstrate that time-varying magnetic fields alter [Ca2+]i and suggest that at least some of the reported biological effects of time-varying magnetic fields may arise from elevation of [Ca2+]i.

Mathematical Modelling of Magneto-Hydrodynamic Dampers With Time-Varying Fluid Properties

2005 ◽  
Author(s):  
Mario F. Letelier ◽  
Dennis A. Siginer ◽  
Jean-Paul Rouliez ◽  
Omar F. Corral
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Yield Stress ◽  
Time History ◽  
Field Variation ◽  
Time Varying ◽  
Viscosity Change ◽  
Flow Equations ◽  
Fluid Properties ◽  
Analytical Tools

The fluid dynamics of dampers is investigated for the case where the damping fluid flows through passages in which a magnetic field is applied. This is a specific case of a new and promising field of applications that has emerged through the design of devices that take advantage of some properties of the so-called electrorheological fluids and magnetorheological fluids (ERF and MRF). These fluids are created when a base fluid is seed with very small dielectric or iron particles, so that it reacts to electric or magnetic fields by developing some non-Newtonian characteristics, most prominently a yield stress, viscosity change, and also viscoelasticity. These fluid properties can be controlled through control of the electric or magnetic fields’ strength. In this paper, a typical damping load is modeled and related to the required flow of a MRF inside the damper. To this end the fluid is modeled as a Bingham fluid with time-varying yield-stress. The analysis here developed makes it possible to determine the magnetic field variation necessary in order to achieve a specific displacement of the damper’s piston. The flow equations are analytically solved for any time-history of the dimensionless fluid’s yield-stress. Main results are some simplified relationships that correlate damping load and magnetic field time-variations. These results aim at providing analytical tools that may facilitate dampers’ design.

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