THE MAGNETIC FIELD

Recent laboratory and epidemiological results have stimulated interest in the hypothesis that human beings may exhibit biological responses to magnetic and/or electric field transients with frequencies in the range between 100 Hz and 100 kHz. Much can be learned about the response of a system to a transient stimulation by understanding its response to sinusoidal disturbances over the entire frequency range of interest. Thus, the main effort of this paper was to compare the strengths of the electric fields induced in homogeneous ellipsoidal models by uniform 100 Hz through 100 kHz electric and magnetic fields. Over this frequency range, external electric fields of about 25-2000 V/m (depending primarily on the orientation of the body relative to the field) are required to induce electric fields inside models of adults and children that are similar in strength to those induced by an external 1 microT magnetic field. Additional analysis indicates that electric fields induced by uniform external electric and magnetic fields and by the nonuniform electric and magnetic fields produced by idealized point sources will not differ by more than a factor of two until the sources are brought close to the body. Published data on electric and magnetic field transients in residential environments indicate that, for most field orientations, the magnetic component will induce stronger electric fields inside adults and children than the electric component. This conclusion is also true for the currents induced in humans by typical levels of 60 Hz electric and magnetic fields in U.S. residences.

In this paper, both electric field and magnetic field were used to assist the hot filament chemical vapor deposition (HFCVD) and we systematically investigated the effects of which on the (1) phase composition, (2) grain size, (3) thickness and (4) preferred orientation of diamond films through SEM, Raman and XRD. The application of magnetic field in electric field, so called ‘the magnetic and electric coupling fields’, enhanced the graphitization and refinement of diamond crystals, slowed down the decrease of film thickness along with the increase of bias current, and suppressed diamond (100) orientation. During the deposition process, the electric field provided additional energy to HFCVD system and generated large number of energetic particles which might annihilate at the substrate and lose kinetic energy, while the Lorentz force, provided by magnetic field, could constrict charged particles (including electrons) to do spiral movement, which prolonged their moving path and life, thus the system energy increased. With the graphitization of diamond films intensified, the preferred orientation of diamond films completely evolved from (110) to (100), until the orientation and diamond phase disappeared, which can be attributed to (I) the distribution and concentration ratio of carbon precursors (C2H2 and CH3) and (II) graphitization sequence of diamond crystal facets. Since the electron field emission property of carbon film is sensitive to the phase composition, thickness and preferred orientation, nano- carbon cones, prepared by the negative bias current of 20 mA and magnetic field strength of 80 Gauss, exhibited the lowest turn-on field of 6.1 V −1 μm−1.

Electromagnetic Environment Associated with Lightning Strikes to Tall Strike Objects

When we move the Hall component in a uniform gradient magnetic field under the constant current, the Hall electromotive force it outputs depends only on the amount of its displacement in the magnetic field. According to this characteristic, this paper analyses the basic principles, the selection of uniform gradient magnetic field and the output of displacement expression data. This paper makes a research from the four aspects. With improvement and innovation, we try to design a sensor which can measure miniature vibration. Introduction Nowadays, as the deepening of the scientific research, we have become increasingly demanding for the accuracy of measurements. That, how to measure small vibrations conveniently and quickly, is a research aspect that receives much concern. Hall displacement sensor, compared with other displacement sensors, has features such as quick response, simple structure and low cost, and some disadvantages about the measurement as well. To achieve the effect small vibrations to be measured, we will improve and research the sensor, based on its disadvantages. Fundamental principles Hall effect When a magnetic field is present to the semiconductor that is perpendicular to the direction of the current, the electrons and holes inside the semiconductor will experience a force, which is called the Lorentz force, and the electrons and holes will accumulate on one face of the material, establishing an electric field. The force from the electric field opposes the Lorentz force. When the electric field reaches a certain value, the electric force and the Lorentz force experienced by the holes and electrons are balance. The electric field opposes the migration of further charge, so a steady electrical potential is established, making the subsequent electron and holes can pass without deflection. This is called the Hall effect. As is shown in the Fig.1. Suppose the conductor is a cuboid, whose length, width and height are a, b, and c respectively, the electricity flows in from surface cd vertically, and that the magnetic field intensity is B vertical to surface ab, the voltage between the two boards front and back is therefore Hall voltage Fig.1: Hall effec International Power, Electronics and Materials Engineering Conference (IPEMEC 2015) © 2015. The authors Published by Atlantis Press 969 According to the formula of Hall voltage U, with a fixed electric current I, as long as the magnetic field gradient is constant, the value of Hall voltage across the Hall element will show a positive liner relationship with its displacement within the Hall element. Hall element. Produce Hall element using the principle of Hall Effect. The performance curve of Hall element is as follows: The purpose is to find appropriate electric current and magnetic field, so that with a fixed electric current and constant magnetic field gradient, the Hall element will work with in interval AB in the phase diagram. The working status of Hall element is also associated with temperature. For the sake of measuring accuracy, SS495A1 Hall element is chosen, whose working temperature is between -40C and 150C with strong flexibility, matching the requirement of measurement and design. . Fig.2: Characteristic Choosing the magnetic field As is shown in the first step, in order to make the instrument reflect tiny vibration, a liner relationship between Hall voltage and displacement is in need. Thus, we need to select a magnetic field with constant gradient. This essay develops the study according to an experiment – correction verify procedure, fitting Hall voltage and displacement of Hall elements in magnetic field of various shapes, through which we find that magnetic field of bar magnet is pretty close. Consequently, we made further improvement based on this idea, and finally choose to fix two angel-shaped iron on the two sides of the bar. The specific measuring method is as follows: Fig.3 Measuring method Fitting this set of data using MATlAB, we have Fig.4:

Calculation of electric and magnetic induced fields in humans subjected to electric power lines

Based on the results of field measurements, during which exceedances of maximum permissible levels of electric field strength (up to 11.5 kV/m) were recorded, mathematical models of the ecological situation of electric and magnetic fields of industrial frequency near the passage of ultra-high voltage power lines have been developed. The combined effect of ultra-low-frequency electric and magnetic fields on the human body in the context of the density of induced currents in organs has been analyzed. Special attention is paid to the analysis of organ systems that are most exposed to the biological effects of the factor. Modeling with the use of human phantom revealed the density of induced currents in the nervous, visual, endocrine systems exceeding the norms (up to 161.5247 mA/m²). The analysis of gradation of the factor influence depending on the location of a person directly from the source of electric and magnetic fields of industrial frequency has been carried out and it has been confirmed that the greatest influence occurs under the projection of the middle phase under the maximum sag and decreases at removal of a person from the sag to the support itself or to the boundaries of the sanitary protection zone.

Electro-optic and magneto-optic modulations of Goos-Hänchen effect in double graphene coating waveguide with sensing applications

Electric and magnetic fields (EMF) are ubiquitous. The earth has static electric fields, which produce lightning during thunderstorms, and geomagnetic fields created by electric currents within its core. Electric and magnetic fields are also produced during electric power generation, transmission, and use.Electric power has generally been considered safe during the more than 100 years of its use, although shocks and burns from direct contact with electrical conductors are a recognized health hazard. Of the approximately 1100 deaths from electric shock that occur each year in the United States, about three‐fourths result from unsafe operation of household appliances; accidents in the workplace account for the rest. The possible health consequences of electric and magnetic field exposure are a much more recent concern.Power‐frequency EMF exposure—unavoidable since the use of electricity has spread throughout the world—has been under investigation since the early 1970s. Investigations have included epidemiologic as well asin vitroandin vivolaboratory studies encompassing a wide range of diseases. The literature on EMF and health is vast, comprising over 1000 published studies, and has been reviewed in depth by several authoritative committees. Of note are reviews by the National Research Council of the National Academy of Sciences (NAS), the National Institute of Environmental Health Sciences (NIEHS) and the U.K. National Radiological Protection Board (NRPB).Electric power systems in the United States, Canada, and Mexico generate and transmit electricity as alternating current (ac), which oscillates at a frequency of 60 cycles per second, or 60 hertz (Hz). Most of the rest of the world generates power at 50Hz. Power‐frequency 50‐ and 60‐Hz fields occupy the extremely low‐frequency (ELF), nonionizing range of the electromagnetic spectrum. The ELF range includes frequencies from 3 to 3000Hz. Above 3000Hz are, in order of increasing frequency or decreasing wavelength, radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, x‐rays, and gamma rays. Microwaves have enough photon energy to heat tissue; ionizing radiation like x‐rays and gamma rays can damage biological systems by breaking chemical bonds. Extremely low‐frequency electric and magnetic fields can neither break bonds nor heat tissue, and the electric currents they induce in the body are very weak.Power‐frequency fields have very long wavelengths of about 5000km. Exposure distances are much shorter than this wavelength; under these circumstances, electric and magnetic fields are independent.Electric field strength increases with increasing voltage, or electric potential; magnetic field strength increases with increasing current. Both electric and magnetic fields decline rapidly with distance from their source, with a faster decline of fields from point sources such as machinery and a slower decline of fields from power lines. Electric fields are further reduced when shielded by conducting objects like buildings and have little penetrative ability; magnetic fields, on the other hand, are capable of penetrating tissue and are not easily shielded.Occupational exposure to electric and magnetic fields occurs from proximity to large motors as well as from wiring in buildings and the use of computers, office machines, and heating and air conditioning systems. Power transmission and distribution facilities are other sources.Accurate assessment of EMF exposure has presented many difficulties in epidemiologic studies and continues to be a considerable challenge. EMF have several unique characteristics that make them more difficult to measure than most other types of exposures. EMF are not readily detectable, are variable in time and space, and are to some extent present in all environments. Additionally, electric fields are both perturbed and intensified by conducting objects like the human body, so that fields measured at various points on the body's surface have different values. Because of the complexity of exposure circumstances, exposure reports from workers are not reliable.

Some functional fluids that respond to both magnetic and electric fields have been prepared and their characteristics are described. In this study, an electro-magnetorheological fluid (EMRF) dispersing zeolite particles containing metallic iron by reducing precipitated magnetite has been investigated. When the viscosity is measured by cone plate viscometer and cylindrical viscometer, electric and magnetic fields are applied both between cone and plate or two cylinders. In case of cone plate, the shear stress at constant shear rate increased with the increase of both magnetic field and electric field. On the other hand when the viscosity is measured by cylindrical viscometer, the shear stress at constant shear rate increased with the increase of electric field, however, the increase rate of shear stress by magnetic field is very small. In this case the magnetic field direction is perpendicular to electric field. The EMRF has typical characteristics to respond with magnetic and electric field. The shear stress of EMRF in electric field is stronger than that of magnetic field. Additionally, the inflection and peak point in the shear rate-shear stress curve are appeared and the behaviors of the clusters in the electric field are observed. The experimental results suggested that the fluid viscosity (shear stress/shear rate) is affected by the arrangement of clusters parallel or perpendicular to the direction of the EMRF flow.

Some functional fluids that respond to both magnetic and electric fields have been prepared and their characteristics are described. In this study, an electro-magnetorheological fluid (EMRF) dispersing zeolite particles containing metallic iron by reducing precipitated magnetite has been investigated. When the viscosity is measured by cone plate viscometer and cylindrical viscometer, electric and magnetic fields are applied both between cone and plate or two cylinders. In case of cone plate, the shear stress at constant shear rate increased with the increase of both magnetic field and electric field. On the other hand when the viscosity is measured by cylindrical viscometer, the shear stress at constant shear rate increased with the increase of electric field, however, the increase rate of shear stress by magnetic field is very small. In this case the magnetic field direction is perpendicular to electric field. The EMRF has typical characteristics to respond with magnetic and electric field. The shear stress of EMRF in electric field is stronger than that of magnetic field. Additionally, the inflection and peak point in the shear rate-shear stress curve are appeared and the behaviors of the clusters in the electric field are observed. The experimental results suggested that the fluid viscosity (shear stress/shear rate) is affected by the arrangement of clusters parallel or perpendicular to the direction of the EMRF flow.

Excitable tissue, when activated, will be found to generate currents both within itself and also in all surrounding conducting media. Volume conductor is usually assumed to be a monodomain, isotropic, resistive, and homogeneous. This chapter considers the properties of the volume conductor as it pertains to the evaluation of electric and magnetic fields. The electric and magnetic field sources are described as a function of position and time, which has the dimensions of current per unit area or dipole moment per unit volume. Sources may also be established exogenously, as exemplied by electric or magnetic field stimulation. The chapter focuses on a description of the volume conductor as it affects the electric and magnetic fields that are established in it.

The transversal wave nature of light was confirmed by studies of electric and magnetic phenomena carried out during the late in nineteenth century. Furthermore, light was found to be an electromagnetic wave. These studies led to laws which established the link between the sources of electric and magnetic fields and these fields itself. J.K. Maxwell was able to find his famous set of equations for the properties of the electric field strength E and the magnetic induction B.

Electromagnetic induction in the Earth’s interior is an important contributor to the near-Earth magnetic and electric fields. The oceans play a special role in this induction due to their relatively high conductivity which leads to large lateral variability in surface conductance. Electric currents that generate secondary fields are induced in the oceans by two different processes: (a) by time varying external magnetic fields, and (b) by the motion of the conducting ocean water through the Earth’s main magnetic field. Significant progress in accurate and detailed predictions of the electric and magnetic fields induced by these sources has been achieved during the last few years, via realistic three-dimensional (3-D) conductivity models of the oceans, crust and mantle along with realistic source models. In this review a summary is given of the results of recent 3-D modeling studies in which estimates are obtained for the magnetic and electric signals at both the ground and satellite altitudes induced by a variety of natural current sources. 3-D induction effects due to magnetospheric currents (magnetic storms), ionospheric currents (Sq, polar and equatorial electrojets), ocean tides, global ocean circulation and tsunami are considered. These modeling studies demonstrate that the 3-D induction (ocean) effect and motionally-induced signals from the oceans contribute significantly (in the range from a few to tens nanotesla) to the near-Earth magnetic field. A 3-D numerical solution based on an integral equation approach is shown to predict these induction effects with the accuracy and spatial detail required to explain observations both on the ground and at satellite altitudes.

This study aims to clarify the frequency characteristics of the spatial distribution of electromagnetic noise inside a distance of 3 m around a printed circuit board (PCB) by simulation and experiment. It is also shows that the finite difference time domain method (FDTD method) is a useful tool to estimate the frequency characteristic of the spatial distribution for the electric and magnetic field around the PCB. By comparison between the electric and magnetic near field spectrum above the printed line by simulation, these spectra are shown to have differences in the resonance frequency: when the characteristics of the electric and magnetic field strength at 60 ns after the excitation is calculated, the electric field is decreased, the magnetic field is not decreased, as the distance from PCB is farther. From the characteristics of particular frequencies, the electric field spectrum at 3 MHz, i.e, clock pulse, is decreased, whereas the magnetic field is not decreased. The electric and magnetic field strength at the resonance frequency, 417 MHz, is decreased in inverse proportional to the square of the distance. It is also clear that the low frequency magnetic field strength may be superior to higher frequency.

The generation of Lorentz force is limited by the local magnetic field and the relative velocity of the spacecraft. As a result of this constraint, the Lorentz force cannot completely take place of the traditional propulsion technologies. In recent years, studying the Lorentz force provided by modulating spacecraft electrostatic charge (magnetic and electric fields) has become a possible good means to control the spacecraft without fuel consumption or reduce the fuel cost. Most of the previous studies concerned the Lorentz force of the magnetic field only. In this paper, we developed a combination of Lorentz forces provided by modulating spacecraft's electrostatic charge (magnetic and electric fields) that can be used to keep the desired relative distances and orientations. We are derived nonlinear dynamic models of satellite relative motion considering J2 perturbation, and Lorentz forces to develop a mathematical model for a new technique establishing increase the level of charging in the spacecraft surface. These solutions indicate that the principal effects of the Lorentz force on a spacecraft can be used to correct the drift in the relative position of formation flying due to the effect of Second zonal harmonics, where the magnitude of charge to mass ratio is the key player for the correction of this drift. Numerical results for different examples of formation flying confirmed the capability of Lorentz force to correct the drift in relative position. These corrections depend on the value of charge to mass ratio and magnitude of the relative position.