European Journal of Physics最新文献_第10页

Should you walk, run or sprint in the rain to get less wet? 你应该在雨中散步、跑步或冲刺来减少淋湿吗?

4区教育学

European Journal of Physics Pub Date : 2023-10-25 DOI: 10.1088/1361-6404/ad06bf

Matteo Zaegel, Mathis Vehils-Vinals, Hugo Guastalla, Benjamin Benabou, Auguste Gires

引用次数: 0

Quantum computing with trapped ions: a beginner's guide 捕获离子的量子计算:初学者指南

4区教育学

European Journal of Physics Pub Date : 2023-10-25 DOI: 10.1088/1361-6404/ad06be

Francesco Bernardini, Abhijit Chakraborty, Carlos R Ordonez

引用次数: 0

Study on the Magnetic Levitation of a Magnetic Flea 磁性跳蚤的磁悬浮研究

4区教育学

European Journal of Physics Pub Date : 2023-10-19 DOI: 10.1088/1361-6404/acfd23

Yuchen Jiang, Jin Wang, Xiaojie Wang

{"title":"Study on the Magnetic Levitation of a Magnetic Flea","authors":"Yuchen Jiang, Jin Wang, Xiaojie Wang","doi":"10.1088/1361-6404/acfd23","DOIUrl":"https://doi.org/10.1088/1361-6404/acfd23","url":null,"abstract":"Abstract We investigated the problem of ‘magnetic levitation’ originating from the <?CDATA $33mathrm{rd}$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:mn>33</mml:mn> <mml:mi>rd</mml:mi> </mml:math> International Young Physicists’ Tournament (IYPT). The problem was first investigated by a PRL paper (Baldwin et al. ) in 2018, which states that the flea of a magnetic stirrer spinning fast enough in a liquid with a high viscosity coefficient can jump from the bottom and levitate stably. The magnetic force and gravity balance periodically. This phenomenon includes several concepts: magnetic dipoles, rigid-body rotation, fluid mechanics and magnetic levitation. They are more or less unfamiliar to undergraduate students. However, the movement of the flea could be described with a concise forced vibration equation, which is familiar in textbooks. The phenomenon could be divided into two stages: synchronous movement and levitation state. The transition is the jumping of the flea. We demonstrated this process and presented several equations to build this physical model. The progression of the phenomenon is due to the increase in the drive magnet angular velocity called the drive velocity. We verified our theory by simulation and experiments. Several parameters are experimentally verified to influence the phenomenon. We also discussed the origin of dynamic stabilization, which would be slightly complicated but worthy for students. In short, we introduce an interesting problem originating from the PRL paper that can be easily achieved under laboratory conditions. We extend some content in a pedagogical way that would be helpful for students to understand the related physical concepts, such as the influence of the viscosity coefficient of the liquid on the flea’s motion, which is not discussed in the PRL paper.","PeriodicalId":50480,"journal":{"name":"European Journal of Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135667264","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"教育学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Pressure Gradient in an Incompressible Fluid as a Reaction Force and the Preservation of the Principle of `Cause and Effect` 不可压缩流体中的压力梯度作为反作用力与“因果”原理的保持

4区教育学

European Journal of Physics Pub Date : 2023-10-17 DOI: 10.1088/1361-6404/acfdd9

Lachezar Slavchev Simeonov

{"title":"Pressure Gradient in an Incompressible Fluid as a Reaction Force and the Preservation of the Principle of `Cause and Effect`","authors":"Lachezar Slavchev Simeonov","doi":"10.1088/1361-6404/acfdd9","DOIUrl":"https://doi.org/10.1088/1361-6404/acfdd9","url":null,"abstract":"Abstract When considering the motion of an incompressible fluid, it is common practice to take the curl on both sides of the Navier–Stokes (or Euler) equations and cancel the pressure force. The governing equations are sufficient to derive the velocity field of the fluid without any knowledge of the pressure. In fact, the pressure is only calculated after obtaining the velocity field. This raises a number of conceptual problems. For instance, why is the pressure unnecessary for obtaining the velocity field? Traditionally, forces have been considered as the ‘causes’ of motion, and the resulting acceleration as the ‘effect’. However, the acceleration (the effect) and the resulting velocity field can be obtained without any recourse to the pressure (the cause), seemingly violating the principle of ‘cause’ and ‘effect’. We address these questions by deriving the pressure force of an incompressible fluid, starting from d’Alembert’s principle of virtual work, as a ‘reaction force’ that maintains the incompressibility condition. Next, we show that taking the curl on both sides of the Navier–Stokes (or Euler) equations is equivalent to using d’Alembert’s principle of virtual work, which cancels out the virtual work of the pressure gradient. This shows that abstract procedures, such as taking the curl on both sides of an equation, can actually be tacit applications of rich physical principles, without one realizing it. This can be quite instructive in a classroom of undergraduate students.","PeriodicalId":50480,"journal":{"name":"European Journal of Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135945122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"教育学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Percolation of 'Civilisation' in a Homogeneous Isotropic Universe “文明”在均匀各向同性宇宙中的渗透

4区教育学

European Journal of Physics Pub Date : 2023-10-17 DOI: 10.1088/1361-6404/acfbc5

Allan Lambit Alinea, Cedrix Jadrin

{"title":"Percolation of 'Civilisation' in a Homogeneous Isotropic Universe","authors":"Allan Lambit Alinea, Cedrix Jadrin","doi":"10.1088/1361-6404/acfbc5","DOIUrl":"https://doi.org/10.1088/1361-6404/acfbc5","url":null,"abstract":"Abstract In this work, we consider the spread of a ‘civilisation’ in an idealised homogeneous isotropic universe where all the planets of interest are habitable. Following a framework that goes beyond the usual idea of percolation in common undergraduate computational physics textbooks, we investigate the behaviour of the number of colonised planets with time, and the total colonisation time for three types of universes. These include static, dark energy-dominated, and matter-dominated universes. For all these types of universes, we find a remarkable fit with the Logistic Growth Function for the number of colonised planets with time. This is in spite of the fact that for the matter- and dark-energy dominated universes, the space itself is expanding. For the total colonisation time, T , the case for a dark energy-dominated universe is marked with divergence beyond the linear regime characterised by small values of the Hubble parameter, H . Not all planets in a spherical section of this universe can be ‘colonised’ due to the presence of a shrinking Hubble sphere. In other words, the recession speeds of other planets go beyond the speed of light making them impossible to reach. On the other hand, for a matter-dominated universe, while there is an apparent horizon, the Hubble sphere is growing instead of shrinking. This leads to a finite total colonisation time that depends on the Hubble parameter characterising the Universe; in particular, we find T ∼ H for small H and T ∼ H 2 for large H .","PeriodicalId":50480,"journal":{"name":"European Journal of Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135944288","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"教育学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

(Avoided) crossings in the spectra of matrices with globally degenerate eigenvalues (避免)具有全局退化特征值的矩阵谱中的交叉

4区教育学

European Journal of Physics Pub Date : 2023-10-17 DOI: 10.1088/1361-6404/acfbc4

Sam Silliman, Mishkatul Bhattacharya

{"title":"(Avoided) crossings in the spectra of matrices with globally degenerate eigenvalues","authors":"Sam Silliman, Mishkatul Bhattacharya","doi":"10.1088/1361-6404/acfbc4","DOIUrl":"https://doi.org/10.1088/1361-6404/acfbc4","url":null,"abstract":"Abstract (Avoided) crossings are ubiquitous in physics and are connected to many physical phenomena such as hidden symmetries, the Berry phase, entanglement, Landau–Zener processes, the onset of chaos, etc. A pedagogical approach to cataloging (avoided) crossings has been proposed in the past, using matrices whose eigenvalues avoid or cross as a function of some parameter. The approach relies on the mathematical tool of the discriminant, which can be calculated from the characteristic polynomial of the matrix, and whose roots as a function of the parameter being varied yield the locations as well as degeneracies of the (avoided) crossings. In this article we consider matrices whose symmetries force two or more eigenvalues to be degenerate across the entire range of variation of the parameter of interest, thus leading to an identically vanishing discriminant. To show how this case can be handled systematically, we introduce a perturbation to the matrix and calculate the roots of the discriminant in the limit as the perturbation vanishes. We show that this approach correctly generates a nonzero ‘reduced’ discriminant that yields the locations and degeneracies of the (avoided) crossings. We illustrate our technique using the matrix Hamiltonian for benzene in Hückel theory, which has recently been discussed in the context of (avoided) crossings in its spectrum.","PeriodicalId":50480,"journal":{"name":"European Journal of Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135944289","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"教育学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Radioactivity in a bucket 桶中的放射性

4区教育学

European Journal of Physics Pub Date : 2023-10-13 DOI: 10.1088/1361-6404/ad0346

Luis Peralta

{"title":"Radioactivity in a bucket","authors":"Luis Peralta","doi":"10.1088/1361-6404/ad0346","DOIUrl":"https://doi.org/10.1088/1361-6404/ad0346","url":null,"abstract":"Abstract In Radiation Physics classes, point sources are typically used, for which it is relatively easy to describe the signal obtained by a radiation detector, such as the NaI(Tl) scintillation detector. The use of large extended radiation sources is generally avoided due to the mathematical complexity that their description may involve. However, the use of Monte Carlo simulation methods allows this limitation to be overcome. Potassium chloride, containing the 40K isotope, is an ideal candidate for carrying out this type of experiment. The source activity is obtained through the detection of the 1460.8 keV gamma- photon emitted in the 40K decay. In the first experiment, a cylindrical container is used, placing the NaI(Tl) detector in its center and filling the remaining space with potassium chloride. In a second, more complex case, a large radioactive source consisting of a container filled with a mixture of sand and potassium chloride, with the NaI(Tl) detector placed in the center of the mixture, is used. In this case, the mass of potassium chloride is approximately 1/5 of the sand mass. In both experiments, the detection efficiency is obtained by Monte Carlo simulation. A careful analysis of the experimental data allows to obtain a good agreement between the measured and calculated value of the activity.","PeriodicalId":50480,"journal":{"name":"European Journal of Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135853737","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"教育学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A hydraulic energy ﬂow within the moving Earth 在移动的地球内部的水力能量流

4区教育学

European Journal of Physics Pub Date : 2023-10-11 DOI: 10.1088/1361-6404/ad026a

Friedrich Herrmann, Michael Pohlig

{"title":"A hydraulic energy ﬂow within the moving Earth","authors":"Friedrich Herrmann, Michael Pohlig","doi":"10.1088/1361-6404/ad026a","DOIUrl":"https://doi.org/10.1088/1361-6404/ad026a","url":null,"abstract":"Abstract We consider the Earth moving through empty space at 30 km/s (in the sun’s frame of reference). Associated with this motion is a convective flow of kinetic and internal energy. Since there is high pressure inside the earth, and since the earth is moving, there is yet another “hydraulic” energy flow. This latter is what this article is about. Although this energy flow is huge, it is not addressed in the textbooks. The reason is that for the explanation one needs a concept which is not introduced in traditional presentations of classical gravitation: the gravitomagnetic field. The corresponding theory, gravitoelectromagnetism, was formulated in 1893 by Heaviside in analogy to Maxwell's theory of electromagnetism.&#xD;&#xD;We discuss the question of what are the sources and sinks of this hydraulic, non-convective energy flow. To answer the question, we need to study the energy flow density distribution within the gravitational field. In doing so, we will make some interesting observations. The energy flow within the field is twice as large as it should be to transfer the field energy from one side of the Earth to the other. The excess flow goes back through the matter of the Earth.&#xD;&#xD;Since our readers may not be familiar with Heaviside’s theory, we first treat the electromagnetic analogue of our problem and then translate the results to the gravitational situation.","PeriodicalId":50480,"journal":{"name":"European Journal of Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136063101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"教育学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Relativistic Mechanics and Thermodynamics. IV. Thermodynamic processes 相对论力学和热力学。四、热力学过程

4区教育学

European Journal of Physics Pub Date : 2023-10-11 DOI: 10.1088/1361-6404/ad026b

J Güémez, Jose Angel Mier

引用次数: 0

Students' confusions about the electric field of a uniformly moving charge 学生对均匀运动电荷的电场的困惑

4区教育学

European Journal of Physics Pub Date : 2023-10-09 DOI: 10.1088/1361-6404/ad0187

Petar Zugec, Horvatic Davor, Ivica Smolić

引用次数: 0