scholarly journals Development of ideas about "bias current"

2021 ◽  
pp. 8-13
Author(s):  
J. M. Hrokholskyi ◽  
B. A. Sus
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Field ◽  
Electric Field ◽  
Direct Current ◽  
Electric Circuit ◽  
Alternating Current ◽  
Bias Current ◽  
Directed Motion ◽  
Directed Movement ◽  
Direct Electric Current

Purpose. In electrical engineering, radio engineering, such concepts as charge, electric field, magnetic field, electromagnetic field, direct electric current, alternating current are used. These abstract concepts reflect certain real physical phenomena. For example, current is understood as the directed movement of electric charges. However, there is also a conditionally abstract concept of "bias current", which was introduced by Maxwell to explain the passage of current through a section of capacitor where there are no charges. The purpose of the article is to reveal the substantive meaning of this term and to explain the real mechanism of current flow in an electric circuit. Methodology. Analysis of the phenomenon is performed on the basis of such traditional concepts as charge, electric field, magnetic field, electromagnetic field, direct electric current, alternating current. Analysis of the contradiction between the concept of current as a directed movement of charges and the concept of "bias current" as a current without charges is presented. Theoretical coordination of the "bias current "concepts and current as a directed  motion of charges is done.  Findings. It is shown that for all sections of a closed electric circuit, the definition of current as a directed movement of charges is valid only for direct current, when the charges are actually moving in all sections of the circuit. In the circuit with the capacitor, direct current does not flow, because there are no charges in the gap between the plates of the capacitor. However, alternating current occurs, at the moment when the circuit is closed. In the area of the conductor there is a directed movement of charges and the cause of the movement is an electric field, which is variable and occurs together with the alternating magnetic field in all parts of the circuit, including the part of the capacitor where there are no charges. It is shown that in general the concept of current as a directed motion of charges is correct, but conditionally abstract, because in fact the root cause is what is called an electromagnetic field. The concept of bias current is a conditionally abstract expression of the electromagnetic field. Originality. The novelty is that it is possible to understand adequately and non-abstractly the processes that occur in an electric circuit during the passage of current, that no current creates an electric field around the conductor on which charges move, and vice versa, alternating electric field leads to charges ,which are in the conductor areas. Practical value. Understanding the real essence of the term makes it possible to assess correctly the processes occurring in the electrical circuit; gives the answer whether the movement of charges occurs gradually or immediately around the circle when connecting an e.r.s. and closing the circuit. This understanding gives you an idea of what happens when the capacitor electrodes are connected to an e.r.s. and why do the electrons in a conductor come in a directed motion, what is the nature of the force acting on the electrons.

Investigating flexible textile-based coils for wireless charging wearable electronics

2019 ◽  
Vol 50 (3) ◽  
pp. 333-345 ◽  
Author(s):  
Danmei Sun ◽  
Meixuan Chen ◽  
Symon Podilchak ◽  
Apostolos Georgiadis ◽  
Qassim S Abdullahi ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electrical Conductivity ◽  
Electromagnetic Field ◽  
Electric Field ◽  
Dimensional Stability ◽  
Screen Printing ◽  
Wearable Electronics ◽  
Wireless Charging ◽  
The Magnetic Field ◽  
Screen Printed

Smart and interactive textiles have been attracted great attention in recent years. This research explored three different techniques and processes in developing textile-based conductive coils that are able to embed in a garment layer. Coils made through embroidery and screen printing have good dimensional stability, although the resistance of screen printed coil is too high due to the low conductivity of the print ink. Laser cut coil provided the best electrical conductivity; however, the disadvantage of this method is that it is very difficult to keep the completed coil to the predetermined shape and dimension. The tested results show that an electromagnetic field has been generated between the textile-based conductive coil and an external coil that is directly powered by electricity. The magnetic field and electric field worked simultaneously to complete the wireless charging process.

A 4 × 4 array multichannel magnetic stimulation system using submillimeter sized planar square spiral coils: The spatial distribution of electromagnetic field

2022 ◽  
pp. 1-18
Author(s):  
Lei Tian ◽  
Limei Song ◽  
Yu Zheng ◽  
Jinhai Wang
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Field ◽  
Spatial Distribution ◽  
Field Strength ◽  
Electric Field ◽  
Magnetic Stimulation ◽  
Spiral Coil ◽  
Average Magnetic Field ◽  
Stimulation System ◽  
Field Strengths

Multi-coil magnetic stimulation has advantages over single-coil magnetic stimulation, such as more accurate targeting and larger stimulation range. In this paper, a 4 × 4 array multichannel magnetic stimulation system based on a submillimeter planar square spiral coil is proposed. The effects of multiple currents with different directions on the electromagnetic field strength and the focusing zone of the array-structured magnetic stimulation system are studied. The spatial distribution characteristics of the electromagnetic field are discussed. In addition, a method is proposed that can predict the spatial distributions of the electric and magnetic fields when currents in different directions are applied to the array-structured magnetic stimulation system. The study results show that in the section of z = 2 μm, the maximum and average magnetic field strengths of the array-structured magnetic stimulation system are 6.39 mT and 2.68 mT, respectively. The maximum and average electric field strengths are 614.7 mV/m and 122.82 mV/m, respectively, where 84.39% of the measured electric field values are greater than 73 mV/m. The average magnetic field strength of the focusing zone, i.e., the zone in between the two coils, is 3.38 mT with a mean square deviation of 0.18. Therefore, the array-structured multi-channel magnetic stimulation system based on a planar square spiral coil can have a small size of 412 μm × 412 μm × 1.7 μm, which helps improving the spatial distribution of electromagnetic field and increase the effectiveness of magnetic stimulation. The main contribution of this paper is a method for designing multichannel micro-magnetic stimulation devices.

On fluid motions induced by an electromagnetic field in a liquid drop immersed in a conducting fluid

1972 ◽  
Vol 51 (3) ◽  
pp. 585-591 ◽  
Author(s):  
C. Sozou
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Field ◽  
Flow Field ◽  
Electric Field ◽  
Lorentz Force ◽  
Liquid Drop ◽  
Conducting Fluid ◽  
Uniform Electric Field ◽  
Tangential Electric Field ◽  
Set Up

The deformation of a liquid drop immersed in a conducting fluid by the imposition of a uniform electric field is investigated. The flow field set up is due to the surface charge and the tangential electric field stress over the surface of the drop, and the rotationality of the Lorentz force which is set up by the electric current and the associated magnetic field. It is shown that when the fluids are poor conductors and good dielectrics the effects of the Lorentz force are minimal and the flow field is due to the stresses of the electric field tangential to the surface of the drop, in agreement with other authors. When, however, the fluids are highly conducting and poor dielectrics the effects of the Lorentz force may be predominant, especially for larger drops.

scholarly journals Electrical conductivity of plasma in magnetic configurations of the sunspots

2019 ◽  
pp. 29-34
Author(s):  
V. Krivodubskij
Keyword(s):  
Magnetic Field ◽  
Electrical Conductivity ◽  
Magnetic Fields ◽  
Electric Field ◽  
Energy Release ◽  
Electric Circuit ◽  
The Sun ◽  
Turbulent Environment ◽  
Strong Magnetic Fields ◽  
Electromagnetic Models

The main problem of electromagnetic models of flares on the Sun is that in conditions of high electrical conductivity of the solar plasma it is difficult to provide an effective energy release as a result of Joule dissipation of currents in the “kernel of the flare”. In order to explain the rapid dissipation of electric currents in the “kernel of the flare”, we, within the framework of macroscopic magnetohydrodynamics, have considered the effect of reducing the electrical conductivity in a turbulent environment. The idea of redistribution of the electrical conductivity in groups of sunspots with complex magnetic field configuration is proposed. The proposed concept for the redistribution of electrical conductivity is based on the following physical effects and well-known observational conditions in the solar atmosphere. 1. Decreasing of the electrical conductivity (increase in the resistivity) in a turbulent environment. 2. Magnetic inhibition of the turbulence under the influence of magnetic fields. 3. Excitation of a large-scale electric field by macroscopic movements of the plasma in the photosphere in the presence of a weak general magnetic field of the Sun (photosphere dynamo). 4. Observed spatial heterogeneous structure of magnetic configurations in the vicinity of groups of sunspots, which leads to the formation of the current layers with the zero (neutral) magnetic fields. In the places of the zero magnetic field in the photosphere (which correspond to the “kernel of the flare”), where there is no suppression of turbulence by magnetism, the conductivity is turbulent in the nature. At the same time, in the vicinity of the sunspots outside the “kernel of the flare”, turbulent motions are largely suppressed by strong magnetic fields (B ≈ 3000 G), which almost alleviates the effect of the influence of turbulence on the conductivity of the plasma. Therefore, the electrical conductivity here will be gas-kinetic in the nature, the value of which greatly exceeds the turbulent conductivity. The turbulent conductivity calculated by us in the photosphere σ T ≈ 5 ⋅ 108 CGSE turned out to be 2-3 orders of magnitude smaller than the gaskinetic conductivity σ ≈ 1011 CGSE (in the places of strong magnetic fields). The discovered areas of the abnormal reduced turbulent conductivity in the places of the zero magnetic lines of complex configurations of the sunspot groups can contribute to the efficient dissipation of the electric currents, which provides efficient thermal energy release of the flares. The problem of circulation of two currents in the electric circuit of the corona-photosphere is briefly considered. According to the model of the photosphere dynamo, the convective movements on the photosphere level excite an electric field of magnitude E0 ≈ 10-4 CGSE. In this case, in external areas (in relation to the region of the “kernel of the flare”) of the electric circuit of the corona-photosphere in the places of strong magnetic fields, where the turbulence is almost suppressed, the value of the current will be ja = σ E0 ≈ 107 CGSE. At the same time, in the area of the “kernel of the flare”, where neutral magnetic fields do not affect turbulence, the current value will be much smaller: jT ≈ σ T E0 ≈ 5 ⋅ 104 CGSE. The existence of two sections with different currents in the electric circle of the corona-photosphere may contribute to the spatial division of charges, which in turn may be useful in the further development of the electromagnetic models of the flare.

scholarly journals Recent Progress on Electromagnetic Field Measurement Based on Optical Sensors

Sensors ◽  
2019 ◽  
Vol 19 (13) ◽  
pp. 2860 ◽  
Author(s):  
Jun Peng ◽  
Shuhai Jia ◽  
Jiaming Bian ◽  
Shuo Zhang ◽  
Jianben Liu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Field ◽  
Electric Field ◽  
Magnetic Fluid ◽  
Optical Sensors ◽  
Field Measurement ◽  
Faraday Effect ◽  
Optical Sensing ◽  
Piezoelectric Materials ◽  
Electrostatic Attraction

Electromagnetic field sensors are widely used in various areas. In recent years, great progress has been made in the optical sensing technique for electromagnetic field measurement, and varieties of corresponding sensors have been proposed. Types of magnetic field optical sensors were presented, including probes-based Faraday effect, magnetostrictive materials, and magnetic fluid. The sensing system-based Faraday effect is complex, and the sensors are mostly used in intensive magnetic field measurement. Magnetic field optical sensors based on magnetic fluid have high sensitivity compared to that based on magnetostrictive materials. Three types of electric field optical sensors are presented, including the sensor probes based on electric-optic crystal, piezoelectric materials, and electrostatic attraction. The majority of sensors are developed using the sensing scheme of combining the LiNbO3 crystal and optical fiber interferometer due to the good electro-optic properties of the crystal. The piezoelectric materials-based electric field sensors have simple structure and easy fabrication, but it is not suitable for weak electric field measurement. The sensing principle based on electrostatic attraction is less commonly-used sensing methods. This review aims at presenting the advances in optical sensing technology for electromagnetic field measurement, analyzing the principles of different types of sensors and discussing each advantage and disadvantage, as well as the future outlook on the performance improvement of sensors.

Effect of uniform electromagnetic field on the trajectory of a free jet in a resistant medium proportional to the velocity.

2015 ◽  
Vol 11 (1) ◽  
pp. 2909-2913
Author(s):  
Mercy Amaebi Orukari ◽  
Ngiangia, A. T
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Field ◽  
Velocity Profile ◽  
Electric Field ◽  
Fluid Particle ◽  
Governing Equations ◽  
Free Jet ◽  
Resistant Medium ◽  
Uniform Electromagnetic Field

The effect of electromagnetic field in a resistant medium of a free jet was carried out. The solutions of the governing equations showed that increase in electric field also increases the  velocity profile of the fluid while increase in magnetic field decreases the velocity of the fluid particle. Increase in path angle beyond radian, shows improved location of objects in a resistant medium proportional to the velocity. 

New Developments to Reduce Arc Blow during SMAW of Pipelines

2018 ◽  
Vol 938 ◽  
pp. 96-103 ◽  
Author(s):  
Sergey V. Baklanov ◽  
Anton S. Gordynets ◽  
A.S. Kiselev ◽  
Mikhail S. Slobodyan
Keyword(s):  
Magnetic Field ◽  
Direct Current ◽  
Arc Welding ◽  
Alternating Current ◽  
Shielded Metal Arc Welding ◽  
Electrode Coating ◽  
Current Electrode ◽  
Repair Work ◽  
Metal Arc Welding ◽  
The Magnetic Field

In some cases, magnetic blow does not allow using direct current for shielded metal arc welding. This is especially true for repair work on pipelines after magnetic flaw detection. Alternating current is useful to control magnetic arc blow during welding. The most promising results give technologies using alternating current with a rectangular waveform. However, the advantages of this method have not been used until now. The main goal of this study is to determine the influence of the parameters of the arc on its stability and the metal transfer mode during shielded metal arc welding under perturbing action of the magnetic field. The proposed methodology of experimental research allowed identifying the cause of arc extinction using direct current electrode positive. This is due to displacement of molten droplets of metal by the magnetic field from of the uneven melted electrode coating and its subsequent separation. This problem was solved using alternating current with the square waveform pulse mode at a frequency of 500 Hz. The amplitude-time parameters of the current pulses provide stabilization of the arc and volume of the molten electrode metal.

scholarly journals Schwinger mechanism in electromagnetic field in de Sitter spacetime

2018 ◽  
Vol 168 ◽  
pp. 03002 ◽  
Author(s):  
Ehsan Bavarsad ◽  
Sang Pyo Kim ◽  
Clément Stahl ◽  
She-Sheng Xue
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Field ◽  
Electric Field ◽  
Pair Production ◽  
Production Rate ◽  
De Sitter ◽  
Sitter Spacetime ◽  
Constant Electromagnetic Field ◽  
Electric And Magnetic Fields ◽  
Schwinger Mechanism

We investigate Schwinger scalar pair production in a constant electromagnetic field in de Sitter (dS) spacetime. We obtain the pair production rate, which agrees with the Hawking radiation in the limit of zero electric field in dS. The result describes how a cosmic magnetic field affects the pair production rate. In addition, using a numerical method we study the effect of the magnetic field on the induced current. We find that in the strong electromagnetic field the current has a linear response to the electric and magnetic fields, while in the infrared regime, is inversely proportional to the electric field and leads to infrared hyperconductivity.

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