Lenz's Law Research Articles

A new approach to reduce the leakage flux and electromagnetic force on distribution transformer under unbalanced faults based on finite element method

Summary The short-circuit capacity design of a transformer is one of the most significant and challenging criteria. Electromagnetic forces in transformer winding regions are produced by interaction between the leakage flux and current density. Under short circuit condition when currents increase to 20 times, windings are exposed to very high electromagnetic force. This paper is focused on the reduction of leakage flux and electromagnetic force under fault condition of distribution transformer. This article is composed of two parts. First, Finite Element Methods (FEM) that improved in Ansoft-Maxwell has been used to investigate the leakage flux and electromagnetic forces of three-phase, three leg, 10/0.4-kV, 1000-kVA distribution transformer. Then, to optimal design of transformer under single phase to ground short circuit condition two auxiliary winding was chosen as an active shielding to reduce the radial and axial leakage flux. According to Lenz's law this windings produce a magnetic flux that is the apposite of the leakage flux from an iron-core system. Results indicate that the proposed auxiliary winding remarkably decreased the leakage flux and electromagnetic force in the winding regions. It should be noted that the resultant of main flux is not affected by auxiliary winding. Copyright © 2015 John Wiley & Sons, Ltd.

Current induced vortex wall dynamics in helical magnetic systems

Nontrivial topology of interfaces separating anti-chiral phases in helical magnets result in new effects as they interact with spin polarized current. These interfces or vortex walls consist of a one dimensional array of vortex lines. Topological Hall effect comes as a natural expectation. Also Lenz's law will result in a new damping mechanism in these systems. We study the dynamics of these wall interacting with electric current and use fundamental electromagntic laws to calculate this effect. On the other hand discrete nature of these walls affects their pinning and result in low depinning current density. We predict the value of this currnt using collective pinnng theory. Finally throughout this study we propose possible standard experiments that may distinguish our theoretical findings.

Negative electric susceptibility and magnetism from translational invariance and rotational invariance

Abstract In this work we investigate magnetic effects in terms of the translational and rotational invariances of magnetisation. Whilst Landau-type diamagnetism originates from translational invariance, a new diamagnetism could result from rotational invariance. Translational invariance results in only conventional Landau-type diamagnetism, whereas rotational invariance can induce a paramagnetic susceptibility for localised electrons and also a new kind of diamagnetism that is specific to conducting electrons. In solids, the moving electron shows a paramagnetic susceptibility but the surrounding screening of electrons may produce a new diamagnetic response by Lenz's law, resulting in a total susceptibility that tends to zero. For electricity, similar behaviours are obtained. We also derive the DC-type negative electric susceptibility via two methods in analogy with Landau diamagnetism.

Transformer Impedance Reflection Demonstration

Questions often arise as to how a device attached to a transformer can draw power from the electrical power grid since it seems that the primary and secondary are not connected to one another. However, a closer look at how the primary and secondary are linked together magnetically and a consideration of the role of Lenz's law in this linkage may help to clear up this confusion.

Magnetic fields in an expanding universe

We find a solution to 4D Einstein–Maxwell theory coupled to a massless dilaton field, for all values of the dilaton coupling, describing a Melvin magnetic field in an expanding universe with ‘stiff matter’ equation of state parameter w = +1. As the universe expands, magnetic flux becomes more concentrated around the symmetry axis for dilaton coupling and more dispersed for . An electric field circulates around the symmetry axis in the direction determined by Lenz's law. For a = 0 the magnetic flux through a disc of fixed comoving radius is proportional to the proper area of the disc. This result disagrees with the usual expectation based on a test magnetic field that this flux should be constant, and we show why this difference arises. We also find a Melvin solution in an accelerating universe with w = −7/9 for a dilaton field with a certain exponential potential.

Magnetic pulse welding on the cutting edge of industrial applications

Magnetic Pulse Welding (MPW) applies the electromagnetic principles postulated in the XIXth century and later demonstrated. In recent years the process has been developed to meet highly demanding market needs involving dissimilar material joining, specially involving difficult-to-weld materials. It is a very high speed joining process that uses an electromagnetic force to accelerate one material against the other, resulting in a solid state weld with no external heat source and no thermal distortions. A high power source, the capacitor, a discharge switch and a coil constitute the minimum equipment necessary for this process. A high intensity current flowing through a coil near an electrically conductive material, locally produce an intense magnetic field that generates eddy currents in the flyer according to Lenz law. The induced electromotive force gives rise to a current whose magnetic field opposes the original change in magnetic flux. The effect of this secondary current moving in the primary magnetic field is the generation of a Lorentz force, which accelerates the flyer at a very high speed. If a piece of material is placed in the trajectory of the flyer, the impact will produce an atomic bond in a solid state weld. This paper discusses the fundamentals of the process in terms of phenomenology and analytical modeling and numerical simulation. Recent industrial applications are presented in terms of materials, joint configurations and real examples as well as advantages and disadvantages of the process.

Electromagnetic Induction with Neodymium Magnets

In April 1820, Hans Christian Ørsted noticed that the needle of a nearby compass deflected briefly from magnetic north each time the electric current of the battery he was using for an unrelated experiment was turned on or off. Upon further investigation, he showed that an electric current flowing through a wire produces a magnetic field. In 1831 Michael Faraday and Joseph Henry separately expanded on Ørsted's discovery by showing that a changing magnetic field produces an electric current. Heinrich Lenz found in 1833 that an induced current has the opposite direction from the electromagnetic force that produced it. This paper describes an experiment that can help students to develop an understanding of Faraday's law and Lenz's law by studying the emf generated as a magnet drops through a set of coils having increasing numbers of turns.

Magnetic flux amplification by Lenz lenses

Tailoring magnetic flux distribution is highly desirable in a wide range of applications such as magnetic sensors and biomedicine. In this paper we study the manipulation of induced currents in passive devices in order to engineer the distribution of magnetic flux intensity in a given region. We propose two different approaches, one based on especially designed wire loops (Lenz law) and the other based on solid conductive pieces (eddy currents). The gain of such devices is mainly determined by geometry giving perspective of high amplification. We consistently modeled, simulated, and executed the proposed devices. Doubled magnetic flux intensity is demonstrated experimentally for a moderate aspect ratio.

Two-port network analysis and modeling of a balanced armature receiver

Models for acoustic transducers, such as loudspeakers, mastoid bone-drivers, hearing-aid receivers, etc., are critical elements in many acoustic applications. Acoustic transducers employ two-port models to convert between acoustic and electromagnetic signals. This study analyzes a widely-used commercial hearing-aid receiver ED series, manufactured by Knowles Electronics, Inc. Electromagnetic transducer modeling must consider two key elements: a semi-inductor and a gyrator. The semi-inductor accounts for electromagnetic eddy-currents, the ‘skin effect’ of a conductor (Vanderkooy, 1989), while the gyrator (McMillan, 1946; Tellegen, 1948) accounts for the anti-reciprocity characteristic [Lenz's law (Hunt, 1954, p. 113)]. Aside from Hunt (1954), no publications we know of have included the gyrator element in their electromagnetic transducer models. The most prevalent method of transducer modeling evokes the mobility method, an ideal transformer instead of a gyrator followed by the dual of the mechanical circuit (Beranek, 1954). The mobility approach greatly complicates the analysis. The present study proposes a novel, simplified and rigorous receiver model. Hunt's two-port parameters, the electrical impedance Ze(s), acoustic impedance Za(s) and electro-acoustic transduction coefficient Ta(s), are calculated using ABCD and impedance matrix methods (Van Valkenburg, 1964). The results from electrical input impedance measurements Zin(s), which vary with given acoustical loads, are used in the calculation (Weece and Allen, 2010). The hearing-aid receiver transducer model is designed based on energy transformation flow [electric→ mechanic→ acoustic]. The model has been verified with electrical input impedance, diaphragm velocity in vacuo, and output pressure measurements.This receiver model is suitable for designing most electromagnetic transducers and it can ultimately improve the design of hearing-aid devices by providing a simplified yet accurate, physically motivated analysis.This article is part of a Special Issue entitled “MEMRO 2012”.

Numerical Simulation on the Influence of the Eddy-current Effect on the Magnetization of Steel Pipe at High Speed

According to Lenz's Law, eddy current effect essentially occurs when relative movement happens between steel pipe and axial magnetizing coil in magnetic flux leakage(MFL) testing. The eddy current magnetic field and the magnetizing field magnetize the pipe together, eventually affecting consistency of the MFL signals. The aim is to analyze the affection on the pipe magnetization by eddy-current effect. Firstly, the eddy current distribution equation in the pipe is established based on the Lenz's Law, and moreover the eddy current magnetic field is obtained. Then, the eddy current magnetizing affections on the pipe head, pipe body and pipe tail are analyzed respectively. The direction of the eddy current in the pipe head is opposite to the one of the magnetizing current, which brings about the reduction of magnetization status. However, the eddy current in the pipe tail and the magnetizing current have the same direction, resulting in the increase of the magnetization. For the pipe body, the eddy current has no affection on the magnetization. The finite element simulation was applied to analyze the relationship between the eddy current intensity and the pipe moving speed and the affection of the eddy current on the magnetization of the whole pipe, which supplies the reference of the uniform evaluation for the steel pipe.

A Uniform Rule that Can Replace the Left-Hand Rule and the Right-Hand Rule in Electromagnetics

The left-hand rule and the right-hand rule are widely used in electromagnetics but are often confusing. Based on an analysis of the differences and commonalities of the two rules, a uniform rule using coordinate rotation is proposed to determine the direction of the magnetic force and the induced electromotive force (emf) or the induced current in a static magnetic field. Furthermore, we discuss how to use the uniform rule to determine the direction of the induced emf or current in a moving magnetic field, which is traditionally determined by Lenz's law. The uniform rule is easy to understand and remember.

Literature survey of eddy-current loss analysis in rotating electrical machines

Eddy current is a very important and intriguing phenomenon. A direct result of Lenz's law, it has been an integral part of research on electrical machines. The applications and associated research field of eddy currents are very widespread and virtually impossible to include in a singlestudy. Therefore this study tends to capture research trends in eddy-current loss analysis pertaining to the field of rotating electrical machines only. The research period taken up is from 1892 to 2010. The trends in research and application have been brought out. This study aims to serve as a reference guide to all those interested in the field of eddy-current loss analysis in electrical machines.

Magnetic Braking: A Video Analysis

This paper presents a laboratory exercise that introduces students to the use of video analysis software and the Lenz's law demonstration. Digital techniques have proved to be very useful for the understanding of physical concepts. In particular, the availability of affordable digital video offers students the opportunity to actively engage in kinematics in introductory-level physics.1,2 By using digital videos frame advance features and “marking” the position of a moving object in each frame, students are able to more precisely determine the position of an object at much smaller time increments than would be possible with common time devices. Once the student collects data consisting of positions and times, these values may be manipulated to determine velocity and acceleration. There are a variety of commercial and free applications that can be used for video analysis. Because the relevant technology has become inexpensive, video analysis has become a prevalent tool in introductory physics courses.

Lenz's Law Demonstration Using an Ultrasound Position Sensor

One of the very popular demonstrations used in introductory physics courses to illustrate Lenz's law is the “slowly falling magnet.” In its simplest version it requires only a powerful cylindrical magnet and a metal tube, typically of copper or aluminum. When dropped in the tube the magnet takes significantly longer to reach the other end than a geometrically similar but nonmagnetic object. This demonstration has been adapted for use in large classes using a camera to monitor the magnet as it approaches the end of the tube.1 Small versions that can be used for hands-on experiments also have been developed2 or are available commercially.3 This classical demonstration in its various forms almost never fails to impress first-time viewers.

A simple demonstration of terminal velocity: an experimental approach based on Lenz's law

No abstract

Jumping ring experiment: effect of temperature, non-magnetic material and applied current on the jump height

The jumping ring experiment is an outstanding demonstration of Faraday's laws of electromagnetic induction and also of Lenz's law. A conducting non-magnetic ring is placed over the extended vertical core of a solenoid. When ac power is applied to the solenoid, the ring is thrown off or held in a state of levitation. This phenomenon happens because the induced current in the ring flows in the direction to counter that of the solenoid current. Consequently, two magnetic fields repel each other, giving rise to the jump effect. The induced current is corresponding to the jump height of a ring. In this work, the jump heights of brass, copper and aluminium rings subjected to different parameters such as temperature, vertical length of ring and applied solenoid current were investigated.

Using a PC and external media to quantitatively investigate electromagneticinduction

In this article we describe an experimental learning path about electromagnetic inductionwhich uses an Atwood machine where one of the two hanging bodies is a cylindrical magnetfalling through a plexiglass guide, surrounded either by a coil or by a copper pipe. The firstconfiguration (magnet falling across a coil) allows students to quantitatively study theFaraday–Neumann–Lenz law, while the second configuration (falling through a copperpipe) permits learners to investigate the complex phenomena of induction byquantifying the amount of electric power dissipated through the pipe as a result ofFoucault eddy currents, when the magnet travels through the pipe. The magnet’s fallacceleration can be set by adjusting the counterweight of the Atwood machine sothat both the kinematic quantities associated with it and the electromotive forceinduced within the coil are continuously and quantitatively monitored (respectively,by a common personal computer (PC) equipped with a webcam and by freelyavailable software that makes it possible to use the audio card to convert the PCinto an oscilloscope). Measurements carried out when the various experimentalparameters are changed provide a useful framework for a thorough understanding andclarification of the conceptual nodes related to electromagnetic induction. The proposedlearning path is under evaluation in various high schools participating in theproject ‘Lauree Scientifiche’ promoted by the Italian Department of Education.

More on Faraday's and Lenz's laws - Qualitative demonstrations

A large variety of simple setups for demonstrating Faraday's and Lenz's laws have been described in the literature.1–4 For a few semesters, we tested some of these setups, especially those suggested in Ref. 1, but recently we decided to develop our own version.

Analysis of a magnet falling through a coil connected into a RL circuit

While a small neodymium magnet is falling through a coil connected into an electric circuit, the induced current is recorded by a computer interface device, MBL. We have measured the current characteristics depending on lengths of coil, 3.6cm, 8.0cm, 16cm, and 30cm with the same number of 400 turns with or without a battery. When the magnet falls vertically toward a coil, the magnet is not free falling because the induced current makes magnetic field. Inside the long coil, the magnet is almost free falling because of no induced current, which ends up with an asymmetric shape. Induced electric current in the circuit that an external battery is supplied is less sensitive. This is because of inertia and magnetic field by the dc current. We found the very interesting point that the maximum of   happens inside coil not inlet plane of the coil. 참고문헌 권문호, 최호명 (2009) 전자기 유도 법칙의 정량적 분석을 위한 실험 장치 제작 및 활용 방안 연구, 새물리 58 : 130-137. 송진웅, 김익균, 김영민, 권성기, 오원근, 박종원 (2004) 학생의 물리 오개념 지도. (주) 북스힐. Carpena P (1997) Velocity measurements through magnetic induction. Am. J. Phys. 65: 135‐140. Halliday D (2007) Fundamentals of Physics. John Wiley & Sons Inc. Kingman R, Rowland SC and Popescu S (2002) An experimental observation of Faraday’s law of induction. Am. J. Phys. 70 (6): 595‐598. Nicklin R C (1986) Faraday's law ‐ Quantitative experiments. Am. J. Phys. 54: 422‐428. Pelesko JA, Cesky M and Huertas S (2005) Lenz’s law and dimensional analysis. Am. J. Phys. 73 (1): 37‐39 Planinic M (2006) Assesment of difficulties of some conceptual areas from electricity and magnetism using the Conceptual Survey of Electricity and Magnetism. Am. J. Phys. 74 (12):1143‐1148. Roy MK, Harbola MK and Verma HC (2007) Demonstration of Lenz`s law: Analysis of a magnet falling through a conducting tube. Am. J. Phys. 75 (8): 728–730. Serway RA, Jeweett JW (2008) Physics for Scientists and Engineers with Modern Physics. Cengage Learning Wood LT, Rottmann RM and Barrera R (2004) Faraday's law, Lenz's law, and conservation of energy. Am. J. Phys. 72: 376‐380.

The Voyager Anomaly and the GEM Theory

For over a decade, the Pioneer Anomaly (PA) was an object of study and remains unresolved. Basically it is a sunward constant acceleration of the spacecraft that appeared unambiguously after the satellites passage beyond Saturn. It now appears possible the PA acceleration is the appearance of second, string-like, solution to the Einstein Equations first discussed in the context of charged finite mass charged particle potentials as part of the GEM theory. The exact solution to the metric equations is similar in form to the Schwartzchild Solution but with a positive sign: grr=(1+rG/r)-1 where rG is a characteristic radius corresponding to the Schwartzchild radius. Adopting the approximation that for weak fields the metric becomes a Newtonian gravity potential: grr ≅-2ϕ, a string potential form is obtained in the limit grr ≅1-2ϕ, for r<<rG, grr≅r/rG (1-r/rG…). For the choice rG=cTH, this produces an effective gravity acceleration a ≅ c/TH=8 x 10-10 m/sec2 in agreement with observations. The “turn on” for this potential apparently occurs with the encounter with Jupiter, which raised the spacecraft to above escape velocity. The possible physical meaning of this second metric appearance is found to be a gravitational form of Lenz's law, where objects departing from gravity potentials experience a resistance that keeps them bound at long distances.