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Table of Content
30 March 2022 Volume 41 Issue 3
Thinking and practice of Electrodynamics by taking advantage of information technology
XIE Shuang-yuan, WANG Zu-yuan, NI Zhong-qiang
College Physics. 2022, 41(3): 1. doi:
10.16854/j.cnki.1000-0712.210349
Abstract
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802
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Electrodynamics is the core course of physics major and an important supporting course for training physics talents in the new era. Focusing on the teaching objectives, teaching contents, teaching methods and teaching evaluation of the course, in this paper the thinking and practical research of Electrodynamics are expounded by taking advantage of information technology and adopting online and offline blended learning mode.
Discussion on teaching and learning of multipole analysis
YU Tian, YAO Xin, LIN Fang, QI Jian-qi, ZHANG Zhi-you, NIE Ya, WANG Lei, ZHU Jian-hua, GONG Min
College Physics. 2022, 41(3): 9. doi:
10.16854/j.cnki.1000-0712.210307
Abstract
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1048
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624
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The multipole expansion is an important analysis method, which defines basic and important physical models: electric as well as magnetic multipoles. The representations of the multipole expression, the multipoles, and the interaction between multipoles and an external electromagnetic field are the core aspects of teaching multipole analysis. In this paper, firstly multipole expansions for both the static electric field and the static magnetic field are given, the relationship between their Cartesian representation and spherical harmonics representation is discussed. Secondly, it is emphasized that multipoles are ideal point models based on the equivalent of electromagnetic potential rather than real charge or current distributions. Finally, the forces and torques due to interactions between multipoles and the external field are reviewed.
Asynchronous variation and Lagrange
,
s equation
LEE Chern, XU Li-jia, ZHANG Xiao-ming, MAO Chang-ning, XIE Fang
College Physics. 2022, 41(3): 16. doi:
10.16854/j.cnki.1000-0712.210453
Abstract
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1127
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508
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In the teaching of theoretical mechanics, Lagrange
,
s equation is deduced based on the principle of least action, and the condition of isochronous variation is generally assumed. Here the
Lagrange
,
s
equation is rederived under the condition of asynchronous variation and its physical meaning is explained.
Conformal transformation of steady heat conduction between two parallel eccentric cylindrical walls
SHI Jin-sheng, ZHANG Qiao-zhen
College Physics. 2022, 41(3): 18. doi:
10.16854/j.cnki.1000-0712.210115
Abstract
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570
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500
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The steady heat conduction between two parallel eccentric cylindrical walls is researched using the conformal transformation. By changing the two eccentric cylinders into two concentric cylinders, shape factors of heat conduction between two surfaces of eccentric cylinder
,
s inside and outside walls, two parallel cylinders outside walls and the ground and buried pipe walls are obtained. This work should be beneficial for the calculation of heat transfer rate for correlated problems and presents a novel formulation for studies of such problems.
Discussion on solving the boundary of wedge conductor by image method
WU Ke-na, ZHOU Guo-hua, MA Wen-shuai, LIU Yue-lin
College Physics. 2022, 41(3): 21. doi:
10.16854/j.cnki.1000-0712.210224
Abstract
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861
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358
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The method of images is an easy way to solve the problem of high symmetry electrostatic field boundary value problem. In this paper, the mirroring problem of the wedge boundary conductive system is studied, at this time there are additional conditions in the angle of the conductive wedge α=π/n（n=2,3,4,…）, which is the question point of students in the teaching process. The theoretical basis for solving the electrostatic field by the method of images is the unique theorem, and under the principle of keeping the relationship between boundary condition and edge value unchanged, the mathematical expression of conductive wedge angle is deduced and the reasons for its additional conditions are explained.
An improvement of experiment device for measuring vaporization heat of water at low cost
LI Jin-ying, LIU Shuang, WANG Meng, YANG Yu-xin
College Physics. 2022, 41(3): 23. doi:
10.16854/j.cnki.1000-0712.210215
Abstract
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632
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1773
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The teaching efficiency of college physics experiment is affected due to the large systematic errors in the manually measuring system of water vaporization heat，since the steam condensed severely，the condensate water mixed into the calorimeter and the steam temperature is difficult to be measured accurately.In this paper，the structure of the experimental device is improved.A steam filter with four orifices bulb is selected instead of the traditional steam filter，and the actual steam temperature is measured in it.An electric heating sleeve with adjustable temperature is installed on steam pipe which can prevent vapor condensation.The systematic errors are reduced.The experimental results have shown that the improved device is stable and reliable with low cost and high measurement accuracy.The relative deviation between the measured results and the accepted value can become less than 3% instead of 10.4% before the improvement.
Remote operating system of physical experiment based on internet of things and teaching scheme ——taking the use of oscilloscope as an example
WANG Ai-ji, WANG Yin-shu, BAI Zai-qiao
College Physics. 2022, 41(3): 27. doi:
10.16854/j.cnki.1000-0712.210311
Abstract
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827
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268
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Distance teaching can break the limitation of time and space, and plays an increasingly important role in modern teaching process. Especially during the fight against COVID-19, distance teaching became a necessary means of teaching. For experimental teaching, the operation of instrument is required. In this paper the use of oscilloscope is taken as an example to explore and practice the way of remote-operating physical experiment based on internet of things. The control of instrument is realized through LabVIEW, and the remote operation of instrument is realized by using the Web Sever function in LabVIEW. A website independently developed by Tornado framework in Python programming is adopted to provide an entrance for the management and remote operation of instrument. Free platforms and tools such as online conference, e-classroom and Wechat are integrated to independently build a low-cost and versatile remote experimental operating system. Teaching scheme including video instruction, centralized class and free exercise are also designed.
Elementary excitations and quasiparticles
GUO Xing-yuan, YANG He-jia, KAI Lai, LIANG Jun-qing
College Physics. 2022, 41(3): 32. doi:
10.16854/j.cnki.1000-0712.210410
Abstract
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1009
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1003
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The concept of quasiparticle or elementary excitations can be used to describe the physical properties of a macroscopic object in a low-excited state. Different physical models correspond to different quasiparticles, and these quasiparticles make the complicated multi-body problem easier to deal with. In three or more than three-dimensional space, according to the spin properties of particles, particles with half-integer and integer spin are consistent with Fermi-Dirac statistics and Bose-Einstein statistics, respectively. In 1977, after studying the topological properties of two-dimensional space by Leinaas and Myrheim, a kind of quasiparticle-anyon with the fractional statistics is proposed. With the development of two-dimensional physical systems, anyon has changed from pure theoretical research to practical research object.
Learning analysis and teaching design for mechanics in physics major of colleges
LIU Yi-xuan, SI Zong-guo, GAO Kun
College Physics. 2022, 41(3): 36. doi:
10.16854/j.cnki.1000-0712.210437
Abstract
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1247
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633
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As the first professional course of physics major in colleges, mechanics connects the transformation of teaching mode from middle education to high education, and plays a basic and enlightening role in the teaching of subsequent physics courses. At present, the content and form of mechanics teaching in most colleges can not meet the needs of students well. In this view, by employing questionnaire combined with interview of students of four grades in physics class of Shandong University, it is aimed to understand students recognition for current course content, teaching methods and assessment modes, and to get students expectations and suggestions for the teaching reform of this course. Based on the survey results, a preliminary scheme for the next teaching design is thus proposed.
Analysis on development and evolution of college physics teaching research ——Visualization analysis based on CNKI
LI Jiao-jiao, ZHOU Yu-qing, DONG Ke, WANG Jia-ning
College Physics. 2022, 41(3): 41. doi:
10.16854/j.cnki.1000-0712.210285
Abstract
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738
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480
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This article uses the content analysis method and the Cite Space software to collect and analyze journal papers related to college physics education and teaching research published in China between 2010 and 2020, in order to sort out the development and evolution of college physics education and teaching research in the past ten years. Through basic information processing, research hotspot presentation and frontier evolution analysis of the literature, the following conclusions are drawn: (i) in the field of college physics education and teaching, the output of papers is stable and continuous, but most of the scholars cooperate with their colleagues research within their own universities, and cross-university or cross-border cooperation is rare; (ii) the research hotspots of university physics are closely related to the development of the timelines; (iii) the dark lines of technology development and the governmentoriented open lines “dominate” the change of research hotspots.
Studies on topological invariants of a string-ball chain
LIN Zhi-xing, WANG Zhi-yuan, YANG Tian-hua
College Physics. 2022, 41(3): 51. doi:
10.16854/j.cnki.1000-0712.210324
Abstract
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1372
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345
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As a representative acoustic system，band structure of a periodical string-ball chain has been widely studied.In spectrum measurement，it
,
s noteworthy that a novel，robust class of eigenstates (edge states)，whose energy lies in the band gap and wave function locates at the edge of the system，have been detected.In this paper，the resemblance between the experiment-observed edge states and ones in topological insulator enabled to develop an analogous theory of topological acoustics to study string-ball system.Numerical simulation of topology invariants demonstrates non-trivial topological properties of the experiment system，proving that the observed edge states are topological-protected edge states；Based on numerical results，a brief discussion is given on topological phase transition and transport properties of edge states.
Solution and visualization of forced transverse vibration of rectangular thin films
ZHOU Ji-chen, GUO Qin
College Physics. 2022, 41(3): 56. doi:
10.16854/j.cnki.1000-0712.210203
Abstract
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1212
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1004
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Transverse vibration analysis of membranes is widely used in musical instrument membranes, ear membranes and plant cell membranes. Comparing with free vibration, the study of forced membrane vibration is more practical. In this paper, the vibration problem of a uniform rectangular thin film fixed on all sides is studied by using the Fourier series method and the impulse theorem, the analytical solution of the problem under forced vibration is obtained, and its vibration state is analyzed visually. It is found that the solution of one-dimensional string vibration can also provide a simple and convenient way to solve the problem of two-dimensional bounded membrane vibration, and the membrane vibration will present more abundant characteristics. The impulse theorem solution of the two-dimensional non-homogeneous vibration problem can also be extended to the two-dimensional active (sink) transport problem.
Measuring Stokes parameters and Jones matrix with rotating wave plate
LAI Yu-cheng, HU Xin-yuan, WU Jia-yi, BAI Zai-qiao
College Physics. 2022, 41(3): 61. doi:
10.16854/j.cnki.1000-0712.210186
Abstract
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849
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347
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In this paper, the calculation details of Stokes parameters of polarized light and Jones matrix of polarizing element measured by rotating wave plate are summarized, and an experimental device is built to measure Jones matrix of liquid crystal cell under different voltages.
Faraday pattern in honey solution
ZHANG Ming-jie, WANG Wei, ZHOU Lu-qun
College Physics. 2022, 41(3): 68. doi:
10.16854/j.cnki.1000-0712.210359
Abstract
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668
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223
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The characteristics of Faraday pattern in honey solution driven by periodic external forces are studied in this paper. Comparing with water or xanthan gum solution, the Faraday pattern of honey solution has a high degree of order. It is found that honey solution and xanthan gum solution have similar dynamic characteristics in the weak nonlinear region. The measurement of dispersion relationship shows that the dispersion relationship of honey solution is in agreement with the gravity-surface tension wave theory, but the non-Newtonian viscosity of honey solution causes some differences between the experiment and the theory.
Three problems in Millikan oil drop experiment
XIAO Yong, DONG Jian
College Physics. 2022, 41(3): 73. doi:
10.16854/j.cnki.1000-0712.210281
Abstract
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1021
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1317
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There are still many problems in Millikan oil drop experiment, such as the large deviation of the measured value of the elementary charge, the "objective function method" to solve the problem of the elementary charge, and the use of ultraviolet lamp on oil drops. If it is not handled well, the teaching effect should be affected. In this paper, the large deviation of the measured value of the elementary charge is considered to be related to the accuracy of the reticle of microscope and the fact that the experimenter does not focuses on the oil drop image. The objective function method is of high precision in solving the elementary charge. The usage is sorted out and the difficulties are clarified. Ultraviolet lamp can be used not only to change the electric quantity of oil drop, but also to directly prove the charge quantization by starting from the oil drop with an elementary charge at the beginning, then measuring the balance voltage after each ionization and using the ratio of voltage.
Generation and visualization of phased focused ultrasonic field based on double concave spherical
KONG Ling-hao, LI Jia-qi, ZENG Tian-you, ZENG Yu-feng,
College Physics. 2022, 41(3): 78. doi:
10.16854/j.cnki.1000-0712.210226
Abstract
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814
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546
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Ultrasonic phased array technology has a very significant value in acoustic levitation. Compared with traditional onedimensional single axis acoustic levitation device,a phased focusing principle based on concave spherical with double emitter ultrasonic array is introduced, and a sound field with strong acoustic levitation ability is producd. What is more, the simulation and visual verification of the sound field are also mainly researched. First, its structure is introduced, and the acoustic theories such as phased focusing principle, ultrasonic standing wave suspension mechanism, sound pressure and acoustic radiation force are expounded. Afterward, according to the results of theoretical analysis, with the help of COMSOL multiphysics multi physical field simulation software, the phased focused ultrasonic field is simulated. The phase of each ultrasonic transducer which produces sound field can be controlled independently. Through the actualtime modification of phase, the sound field can be dynamically focused to realize the suspension and arbitrary trajectory movement of particles. Finally, the single reflector schlieren system is used to achieve the realtime visualization of sound field. Compared with the simulation results, the accuracy of the phase controlled focusing principle of the concave spherical double emitter ultrasonic device is verified.
Just Accepted
