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  • Coding closed and open quantum systems in MATLAB: applications in quantum optics and condensed matter
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-29
    Ariel Norambuena, Diego Tancara and Raúl Coto

    We develop a package of numerical simulations implemented in MATLAB to solve complex many-body quantum systems. We focus on widely used examples that include the calculation of the magnetization dynamics for the closed and open Ising model, dynamical quantum phase transition in cavity QED arrays, Markovian dynamics for interacting two-level systems, and the non-Markovian dynamics of the pure-dephasing

    更新日期:2020-06-30
  • A numerical model to introduce students to AC loss calculation in superconductors
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-24
    Francesco Grilli and Enrico Rizzo

    A numerical model implemented in the open-source finite-element method FreeFEM program is presented, with the aim of introducing students to the calculation of AC losses in superconductors. With this simple approach, students can learn about the critical state model used to describe the macroscopic electromagnetic behavior of superconductors and the importance of different factors influencing the AC

    更新日期:2020-06-25
  • On the electrostatic potential and electric field of a uniformly charged disk
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-17
    V Bochko and Z K Silagadze

    We calculate the electrostatic potential and electric field of a uniformly charged disk everywhere in space. This electrostatic problem was solved long ago, and its gravitational analogue was solved even earlier. However, it seems that physics students are not aware of the solution, because it is not presented in textbooks. The purpose of the present article is to fill this gap in the pedagogical literature

    更新日期:2020-06-18
  • Projection operators for asymmetric two-mode coherent states and two-mode Fock states
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-17
    Wang Shuai, Sui Yong-Xing and Zhu Xiao-Qin

    Operators play an important role in the formalism of quantum mechanics. By means of the technique of integration within an ordered product of operators and Dirac notation, we analytically prove that a new kind of asymmetric two-mode projection integral operator and another asymmetric two-mode Fock state projection summation operator are equal to the same Hermitian operator. For such Hermitian operator

    更新日期:2020-06-18
  • Understanding the phenomenon of x-ray diffraction by crystals and related concepts
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-17
    Pablo Aguilar-Marín, Luis Angelats-Silva, Ernesto Noriega-Diaz, Mario Chavez-Bacilio and Ricardo Verde-Vera

    The x-ray diffraction (XRD) technique has become an irreplaceable tool in the study of crystalline solids and is taught as part of the content of undergraduate solid state physics and chemistry courses. The XRD by crystalline materials is a scientific discovery predicted by von Laue, experimentally verified by Friedrich and Knipping and further developed by Bragg and Bragg, father and son, all in 1912

    更新日期:2020-06-18
  • A double well on-line simulation and activities for active learning of introductory quantum mechanics
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-17
    Sergej Faletič

    Teaching introductory quantum mechanics is challenging, especially to students who have limited knowledge of mathematics. The challenges and approaches are evidenced in a wide range of literature. Our goal is to develop an active engagement module for introductory quantum mechanics that would cover the most important concepts: indeterminism, incompatibility, the difference between superposition and

    更新日期:2020-06-18
  • An analysis in the non-inertial frame: ball in a rotating tube and the Taylor column
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-16
    Xinghong Fu

    In this paper, we consider a small ball placed in a liquid-filled transparent cylinder sealed at both ends. When the tube is inclined and spun about the vertical axis like a centrifuge, a heavy ball (more dense than the liquid) will accelerate to either the top or bottom end of the tube depending on its release position while a light ball (less dense than the liquid) will instead tend towards an equilibrium

    更新日期:2020-06-17
  • Defining the electromagnetic potentials
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-16
    Art Davis

    This paper offers a critical examination of the classical method of introducing the elecrtromagnetic potentials in a nonrelativistic context. It applies the nonretarded Helmholtz theorem to show that the usual method is ambiguous, with that ambiguity being reflected in the gauge transformation equations. This ambiguity can be removed by carefully invoking the Helmholtz decomposition theorem, but the

    更新日期:2020-06-17
  • The geodynamo for non-geophysicists
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-15
    Friedrich Herrmann and Tobias Vorbach

    The geodynamo usually appears as a somewhat intimidating subject. Its understanding seems to require knowledge of the intricate theory of magnetohydrodynamics. The solution of the corresponding equations can only be achieved numerically. It seems to be a subject for the specialist. We show that one can understand the basics of the functioning of the geodynamo solely by using the well-known laws of

    更新日期:2020-06-15
  • Neutron interaction with electromagnetic fields: a didactic approach
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-15
    S A Bruce and J F Diaz-Valdes

    In physics, consideration of phenomena in one or two space dimensions (1 + 1 or 2 + 1 space-time dimensions) is often regarded as a useful step toward understanding them in three space dimensions (3 + 1 space-time dimensions). This article presents the basic dynamics of a neutron with a magnetic moment in the presence of certain electromagnetic fields in 2 + 1 space-time dimensions by using a polar

    更新日期:2020-06-15
  • Insights from intracules and Coulomb holes
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-15
    Golam Ali Sekh, Benoy Talukdar and Supriya Chatterjee

    We point out that a typical two-electron distribution function in atoms and molecules, often called the intracule, has a particular sensitivity to the electron–electron repulsion, which leads to the so-called Coulomb correlation. The difference between the intracule densities is computed using the correlated and uncorrelated wave functions, and has been given the name Coulomb hole. The study of intracule

    更新日期:2020-06-15
  • An undergraduate laboratory experiment to accurately measure the speed of light
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-15
    Andrew James Murray

    In 1983 the speed of light was set as an exact quantity. It is now one of the fundamental constants in physics, with the meter being directly related to this speed and the definition of the second. As such, experiments that calculate the speed of light with high precision are important in university undergraduate laboratories. In the experiment discussed here, a method is described that allows the

    更新日期:2020-06-15
  • Projection operators in statistical mechanics: a pedagogical approach
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-15
    Michael te Vrugt and Raphael Wittkowski

    The Mori–Zwanzig projection operator formalism is one of the central tools of nonequilibrium statistical mechanics, allowing one to derive macroscopic equations of motion from the microscopic dynamics through a systematic coarse-graining procedure. It is important as a method in the physical sciences and gives many insights into the general structure of nonequilibrium transport equations and the general

    更新日期:2020-06-15
  • Chirality through classical physics
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-15
    Chris L Lin

    Chirality, or handedness, is a topic that is common in biology and chemistry, yet is rarely discussed in physics courses. We provide a way of introducing the topic in classical physics, and demonstrate the merits of its inclusion—such as a simple way to visually introduce the concept of symmetries in physical law—along with giving some simple proofs using only basic matrix operations, thereby avoiding

    更新日期:2020-06-15
  • Constant power dissipative motion
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-15
    José M Pérez Ramos, Carmen Toro Castillo and Héctor O González Ochoa

    We analyse the velocity of a particle propelled by a constant power and subjected to a dissipative force. We consider three cases of dissipative processes: dry friction and viscous drag in the regime of linear and quadratic dependence on velocity. We derive the equation of motion and then, based on a rational and graphical analysis, determine the qualitative shape of the velocity curve as a function

    更新日期:2020-06-15
  • Exploring the cantilever: teaching tools for atomic force microscopy
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-15
    Merrell A Johnson

    This paper presents a series of experiments that aim to aid with the understanding of some of the fundamental concepts pertaining to the resonance of cantilevers. The goal is to provide an accessible platform for exploring how the cantilever, one of the fundamental components in non-contact scanning probe/atomic force microscopy, is utilized in measuring forces. A straightforward experiment that utilizes

    更新日期:2020-06-15
  • Modelling the dynamics of magneto-mechanical systems through the action principle
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-15
    Rashid Khan and Kåre Olaussen

    We illustrate how the dynamics of a system of moving mechanical objects, in interaction with the electric currents in electromagnets, can be modelled by use of the action principle. After defining the model by a Lagrange function, an internally consistent set of dynamical equations can be derived in a straightforward manner. We also illustrate the philosophy of effective descriptions , where certain

    更新日期:2020-06-15
  • Verdet constant determination of dielectric media using a new versatile, portable and low-cost magneto-optical rotator
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-15
    Watheq Al-Basheer

    The full details of a newly developed versatile, portable and low-cost magneto-optical device for the accurate determination of Verdet constant over the wavelength range of 400–480 nm in undergraduate physics and chemistry labs are presented. The elevated sensitivity of the device is achieved by using a semiconducting photodiode detector coupled with an electronic circuit board, which is configured

    更新日期:2020-06-15
  • Variation theory as a lens for interpreting and guiding physics students’ use of digital learning environments
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-15
    Elias Euler, Bor Gregorcic and Cedric Linder

    In this paper, we examine the implementation of a digital learning environment—namely, the physics software, Algodoo —which is less-constrained in its design than the digital learning environments typically used in physics education. Through an analysis of a case study, we explore a teaching arrangement wherein physics teachers responsively guide small groups of students as they use less-constrained

    更新日期:2020-06-15
  • Impact of a ball with a flexible beam
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-15
    Rod Cross and Crawford Lindsey

    The impact of a ball with a flexible beam is analysed both experimentally and theoretically. The impact generates a bending wave that may or may not return to the impact point before the ball bounces off the beam. If the ball rebounds before the bending wave returns, then the rebound speed of the ball is determined by localised bending of the beam in the vicinity of the impact point. For a short duration

    更新日期:2020-06-15
  • Gas dilution experiment for undergraduate
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-15
    I E Santosa

    This paper presents a simple setup to investigate the continuous gas dilution process. The setup consists of vessels and an oxygen sensor. Two experiments have been conducted. First, by flowing nitrogen (N 2 ) into a vessel containing ambient air, the oxygen (O 2 ) concentration depletes following an exponential decay. The decay constant depends on the vessel’s volume and the flow rate. Second, in

    更新日期:2020-06-15
  • Tunneling times in a taut string
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-02
    Diosdado Villegas, Francisco A Horta-Rangel, Tamé González, Israel Quirós, R Pérez-Álvarez and Fernando de León-Pérez

    The mathematical analogy of classical and matter waves can help to teach the elusive subject of tunneling times in undergraduate physics courses. The tunneling of mechanical energy through a taut string is revisited in this paper in order to study tunneling times for this classical system. General properties of the group delay, the dwell time and the interference time are described. Moreover, we explain

    更新日期:2020-06-02
  • Item response curve analysis of Likert scale on learning attitudes towards physics
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-02
    M G Reyes and S Rakkapao

    The item response curve (IRC) shows the proportion of item responses plotted against total scores achieved in an assessment instrument. It has acquired widespread employment in the field of physics education to analyze tests on physics content knowledge. In the current study, the IRC was lengthened to investigate attitude items of Colorado Learning Attitudes about Science Survey (CLASS) with a five-point

    更新日期:2020-06-02
  • Introducing supersymmetric quantum mechanics via point canonical transformations
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-02
    Gabriel González

    We propose an alternative way to introduce supersymmetric quantum mechanics to physics students using a point canonical coordinate transformation. We provide two point canonical transformations that allow us to obtain new supersymmetric partner Hamiltonians with iso-spectral and non-iso-spectral energy eigenvalues starting from a known solvable Hamiltonian. We illustrate this new approach by applying

    更新日期:2020-06-02
  • Law of inertia, clock synchronization, speed limit and Lorentz transformations
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-02
    J M Aguirregabiria, A Hernández and M Rivas

    In his first 1905 article on special relativity, clock synchronization by means of light rays was used by Einstein to derive the Lorentz transformations ( Ann. Phys., Lpz. 322 891–921). However, the same goal can be achieved by using bodies in free motion to synchronize clocks. To this end, one has to accept the principle of relativity, the law of inertia and the existence of a limit value for the

    更新日期:2020-06-02
  • Generalized potential for apparent forces: the Coriolis effect
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-02
    Elmo Benedetto, Ivana Bochicchio, Christian Corda, Fabiano Feleppa and Ettore Laserra

    It is well known, from Newtonian physics, that apparent forces appear when the motion of masses is described using a non-inertial frame of reference. The generalized potential of such forces is rigorously analyzed, focusing on their mathematical aspects.

    更新日期:2020-06-02
  • Special relativity from classical gedanken experiments involving electromagnetic forces: a contribution to relativity without light
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-02
    Sergio Eduardo Silva Duarte and Nathan Willig Lima

    Our goal is to present a derivation of Lorentz’s transformations from gedanken experiments with electromagnetic forces without having to assume Einstein’s postulate of the constancy of the speed of light. Instead, we propose a different second postulate, namely that electric charge is independent of the state of motion of the system, and we restrict the first postulate in order to state the relativity

    更新日期:2020-06-02
  • Parametric resonance of two coupled spring oscillators driven by a periodic force combined with periodic noise
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-02
    I Zeylikovich and A Nikitin

    In this paper, we describe the instrumentation and theory of the parametric resonance generation of two coupled spring oscillators. We demonstrate the generation of the parametric resonance of coupled oscillators driven by a periodic force combined with periodic noise. We experimentally and theoretically investigated the parametric oscillations and resonances of coupled spring oscillators. Thus, a

    更新日期:2020-06-02
  • Learning to use Cartesian coordinate systems to solve physics problems: the case of ‘movability’
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-06-02
    Trevor S Volkwyn, Bor Gregorcic, John Airey and Cedric Linder

    In this paper, we show that introductory physics students may initially conceptualise Cartesian coordinate systems as being fixed in a standard orientation. Giving consideration to the role that experiences of variation play in learning, we also present an example of how this learning challenge can be effectively addressed. Using a fine-grained analytical description, we show how students can quickly

    更新日期:2020-06-02
  • The benefit of computational modelling in physics teaching: a historical overview
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-04-22
    Jannis Weber and Thomas Wilhelm

    Computational modelling is not only an important element in scientific research, it also has a rich history in physics education and its application in the classroom has changed greatly over the last few decades. To explain why computational modelling is used in physics education, we discuss its use in teaching and the benefits to the teaching and learning process. Secondly, historical developments

    更新日期:2020-04-22
  • Will direct exposure to the Sun damage all digital cameras equally?
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-04-21
    Antonio Agnesi

    Considerations of optical damage induced by thermal effects were initiated by an apparent paradox: small and large diameter lenses with the same f -number produce an image of the Sun with the same irradiance. Thus, if one assumes that a damage threshold is given by irradiance (or intensity, as it is specified by most laser optics companies, in relation to continuous-wave lasers), all digital cameras

    更新日期:2020-04-21
  • Comments on ‘The abrupt ending of a spinning disk’
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-04-21
    Kwang-Hua R Chu

    We make some crucial remarks about the recent presentation by Cross (2019 Eur. J. Phys. 40 065002) for pedagogical purposes considering his results. The possible deformations will influence significantly the role of (high) spots played in an abrupt stop of Euler’s disk as claimed by Cross. We thought Cross should consider the crucial role of the deformations (in a spinning disk as well as the surface

    更新日期:2020-04-21
  • Brownian motion across a magnetic field: Langevin approach revisited
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-04-21
    N Lucero-Azuara, N Sánchez-Salas and J I Jiménez-Aquino

    In this work we present Langevin’s original method to study the Brownian motion of a charged particle across a constant magnetic field. Langevin’s strategy allows one to transform the Langevin equation into a deterministic one associated with mean square displacement (MSD), whose solution is explicitly studied in this work. We calculate the MSD for the z -axis, along which the magnetic field is allowed

    更新日期:2020-04-21
  • On the elliptic locus of a family of projectiles
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-04-21
    Joseph A Rizcallah

    A little-known property of free-fall motion is the elliptic locus of the maximum heights attained by coplanar projectiles launched from a single point in different directions with the same initial speed. Another, less-known, and perhaps somewhat surprising, property of this family consists in the said ellipse being also the geometric locus of the critical points of the projectiles’ distances from the

    更新日期:2020-04-21
  • A little-known minimum concerning resistors in series and in parallel
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-04-21
    Robert Frenkel and Les Kirkup

    In the elementary theory of electrical circuits, the series connection of n identical resistors has an equivalent resistance n 2 greater than the equivalent resistance of their parallel connection. More briefly, the series/parallel ratio is n 2 . We show that if the resistors are not all identical, the series/parallel ratio is greater than n 2 and can never be less than n 2 . This little-known minimum

    更新日期:2020-04-21
  • Physics in the information age: qualitative methods in quantum mechanics
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-04-21
    V G Karpov and Maria Patmiou

    The traditional pedagogical paradigm in physics is based on a deductive approach. However, with the recent advances in information technology, we are facing a dramatic increase in the amount of readily available information. We propose that incorporating inductive elements in teaching—by infusing qualitative methods—will better prepare us to deal with the new information landscape and the realities

    更新日期:2020-04-21
  • Calculating Pauli–Jordan function
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-04-21
    Daqing Liu, Furui Chen, Shuyue Chen and Ning Ma

    A derivation of the space-time expression of the Pauli–Jordan function (PJF) was shown and a more compact result was obtained. Compared to other derivations, the approach utilizes more physical image, such as a Lorentz invariance of the PJF. Furthermore, the approach does not need sophisticated mathematical techniques and is therefore more suitable for the beginner of quantum field theory, such as

    更新日期:2020-04-21
  • On the infinities in the electric potential of unbounded charge distributions
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-04-21
    Douglas Mundarain

    In every beginner electricity and magnetism course, a good teacher usually insists that if one has an infinite charged plate or an infinity charged wire, one must first calculate the electric field to find the potential difference between two space points by making a linear integral of the field. One does it this way because Coulomb’s potential, i.e. the expression which allows for a direct calculation

    更新日期:2020-04-21
  • Charge densities for conducting ellipsoids
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-04-21
    T L Curtright, Z Cao, S Huang, J S Sarmiento, S Subedi, D A Tarrence and T R Thapaliya

    The volume charge density for a conducting ellipsoid is expressed in simple geometrical terms, and then used to obtain the known surface charge density as well as the uniform charge per length along any principal axis. Corresponding results are presented for conducting hyperellipsoids in any number of spatial dimensions. The presentation is at a level suitable for use in graduate courses on electrostatics

    更新日期:2020-04-21
  • Electrostatic responses of anisotropic dielectric films
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-04-21
    Hai-Yao Deng

    We study the electrostatic responses (i.e. retardation effects due to the propagation of electromagnetic waves are ignored) of a linear homogeneous and anisotropic (LHA) dielectric film to an arbitrary external electrostatic potential. A set of algebraic equations has been established to calculate the polarisation charges induced in the film. In our derivation, the idea is exploited that a physical

    更新日期:2020-04-21
  • On the unsteady rotating fluid flow in a uniformly rotating or fixed vertical cylinder
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-04-21
    Vladimir Ivchenko

    In this paper we consider the properties of the transient process that always precedes (or completes) the onset (cessation) of steady fluid flow in a uniformly rotating vertical cylinder. First, we give an elementary (without using the Navier–Stokes equations) and detailed derivation of the equation describing the space and time distribution of angular speeds in a rotating viscous fluid. This expression

    更新日期:2020-04-21
  • Experimental analysis of the free surface of a liquid in a rotating frame
    Eur. J. Phys. (IF 0.756) Pub Date : 2020-04-21
    Martín Monteiro, Fernando Tornaría and Arturo C Martí

    The shape of a liquid surface in a rotating frame depends on the angular velocity. In this experiment, a fluid in a narrow rectangular container is placed on a rotating table. A smartphone fixed to the rotating frame records the fluid surface with its camera and, with a built-in gyroscope, the angular velocity. As the table rotates the surface evolves and develops a parabolic shape. Using video analysis

    更新日期:2020-04-21
  • Improving series convergence: the simple pendulum and beyond.
    Eur. J. Phys. (IF 0.756) Pub Date : 2018-01-01
    Solomon F Duki,T P Doerr,Yi-Kuo Yu

    A simple and easy to implement method for improving the convergence of a power series is presented. We observe that the most obvious or analytically convenient point about which to make a series expansion is not always the most computationally efficient. Series convergence can be dramatically improved by choosing the center of the series expansion to be at or near the average value at which the series

    更新日期:2019-11-01
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