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    20 June 2021 Volume 40 Issue 6
      
    Searching detail and element for improving online teaching quality
    BAO Jing-dong
    College Physics. 2021, 40(6):  1.  doi:10.16854 / j.cnki.1000-0712.210117
    Abstract ( 474 )   PDF (782KB) ( 117 )  
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    By means of the course of thermodynamics and statistical physics,we investigate on the

    challenging problem of online teaching. The motivation,examples and element are discussed. We

    learn Feynman and share ex- perience of editing textbook of thermodynamics and statistical physics

    Solutions for a familiar mechanical problem
    SU Guo-zhen
    College Physics. 2021, 40(6):  5.  doi:10.16854 / j.cnki.1000-0712.200346
    Abstract ( 572 )   PDF (861KB) ( 430 )  
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    New solutions for a mechanical problem relating to the harmonic oscillation are presented based on a deep analysis.
    Application of the formation mechanism of neutronstar to the education of solid state physics
    WANG Shuan-hu, TIAN Ying-yi, WANG Min, DAI Fu-ping
    College Physics. 2021, 40(6):  8.  doi:10.16854 / j.cnki.1000-0712.200413
    Abstract ( 500 )   PDF (805KB) ( 183 )  
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    Based on the discussion of dispersion relation and density of states in solid state

    physics,in this paper,the difference of the dispersion relation of electrons under relativistic and

    non-relativistic limit is studied.The difference eventually leads to a distinct final evolution results of supermassive

    celestial body. The process of theoretical calculation can be easily correlated to the study of electron behavior in solid state physics. Integrating this mechanism into the education of solid state physics can not only enhance the understanding on the electron be-havior in solid state matter,but also provide a deep insight to the relativistic behavior of electron.

    Solving the continuous collisions by the phase space trajectory
    LI Kai-wei
    College Physics. 2021, 40(6):  11.  doi:10.16854 / j.cnki.1000-0712.200420
    Abstract ( 660 )   PDF (764KB) ( 272 )  
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    When two objects occur multiple successive collisions,the solution becomes complicated. This paper proposes the method of phase space trajectory to solve the problem and make the motion process visual. The caculation is also to be easy.
    Uniformity of magnetic field created by four parallel,coaxial and current-carrying square coils of equal size
    ZAN Hui-ping, ZHANG Yin-ke
    College Physics. 2021, 40(6):  14.  doi:10.16854 / j.cnki.1000-0712.200373
    Abstract ( 536 )   PDF (2511KB) ( 92 )  
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    Uniform magnetic field has many applications in scientific research and

    engineering technology. Based on Biot-Savart law and the superposition principle of magnetic

    field,the mathematical expressions of magnet- ic induction intensity created by four

    parallel,coaxial and current-carrying square coils of equal size ( FPCSCS) are derived. By

    using Taylor series expansion method,the conditions,under which the FPCSCS generates a mag-

    netic field of the best uniformity,have been found. The uniformity of magnetic fields

    produced by the FPCSCS in three cases is discussed. The results show that,in the optimum

    situation,the FPCSCS can generate a very homoge- nous magnetic field with magnitude relative

    deviation of less than 0.01% and direction deviation of less than 0.01 degree. Compared

    with the homogenous magnetic fields of square Helmholtz coil,the magnetic field of FPCSCS has

    obvious advantages,which are greater magnitude and better uniformity.

    Application of MATLAB to the study of quantum mechanics
    ZHOU Qun-yi¹, MO Yun-fei², ZHOU Li-li⁴, HOU Zhao-yang³
    College Physics. 2021, 40(6):  19.  doi:10.16854 / j.cnki.1000-0712.200527
    Abstract ( 704 )   PDF (1079KB) ( 329 )  
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    This paper points out some errors in the article of “Commonly using

    mathematical tools in the course of quantum mechanics”and lists the correct formula. There are

    many formulas in quantum mechanics,while the optimal tool for solving calculation problems should

    be MATLAB. In this paper,with help of MATLAB,we have illustrated the algorithm of limit,the

    algorithm of integration,the solution of ordinary differential equations,the representation

    and algorithm of Dirac function,the usage of gamma function and beta function,and the algorithm of

    special functions. One-dimensional linear harmonic oscillator has been taken as an example,which

    can reflect the application of MATLAB in quantum mechanics. MATLAB can also calculate and show the

    graphics about the proba- bility density of the emergence of electrons in hydrogen atoms.

    Applications of time-space diagram to special relativity teaching
    XU Guang-zhi, LI Yi-jie
    College Physics. 2021, 40(6):  26.  doi:10.16854 / j.cnki.1000-0712.200417
    Abstract ( 581 )   PDF (876KB) ( 183 )  
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    This paper introduces the approaches of quantitative calculation using the Minkowski

    time-space di- agram in special relativity. Formulas are derived for velocity addition,light

    Doppler effect,aberration of light and so on.

    A deduction method of mass-velocity relationship in special theory of relativity
    FENG Shi-meng
    College Physics. 2021, 40(6):  32.  doi:10.16854 / j.cnki.1000-0712.200506
    Abstract ( 1052 )   PDF (616KB) ( 289 )  
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    The mass-velocity relationship is an important conclusion of the theory of relativity.

    Most textbooks use two objects to collide completely in-elastically for observing the speed

    change from different frames of refer- ence,and obtain the mass-speed relationship. This paper

    uses the Lorentz transformation of space-time in the spe- cial theory of relativity to prove the

    invariance of the force in the direction of motion in the two inertial reference

    frames. Then,Newton's second law is directly to derive the relationship between mass and

    speed. This derivation method is relatively simple. which is very conducive to the

    understanding of junior college students.

    Understanding time and space connotation of Lorentz transformation by geometry
    ZHANG Liang
    College Physics. 2021, 40(6):  36.  doi:10.16854 / j.cnki.1000-0712.200490
    Abstract ( 670 )   PDF (885KB) ( 239 )  
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    Lorentz transformation is the core content of special relativity. It is of great

    significance to understand and master the conceptual connotation of Lorentz transformation

    for further understanding the space - time view of special relativity. In this paper,the

    nature of time-space transformation called clock slowing and scale reduction and the

    speed of light invariance condition are studied based on the two-dimensional rotation of the

    space-time dia- gram. It enables students to understand the Lorentz transformation more

    intuitively and lays the foundation for subse- quent courses.

    Resistance of physical pendulum system for large swing angular motion
    KANG Xiu-ying
    College Physics. 2021, 40(6):  41.  doi:10.16854 / j.cnki.1000-0712.200529
    Abstract ( 405 )   PDF (1313KB) ( 125 )  
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    In this paper,nonlinear dynamic process of a physical pendulum system with big

    swing angles is explored theoretically and experimentally. By considering the influence of the

    friction and the air resistance,the de- cay process of the pendulum angle and the mechanical energy

    with time is investigated with different initial angles and masses. By comparing with

    the numerical simulation results,the friction coefficient of the rotation axis of the

    physical pendulum and the air resistance coefficient are given as 0.025 and 0.68,respectively. The

    results can pro- vide a reference for dynamic modeling of the pendulum structures such as bearing

    and hinge.

    Influence of the waveform distortion of magnetic field intensity on the shape of AC hysteresis loops
    LV Qing-rong, FENG Shuang-jiu
    College Physics. 2021, 40(6):  45.  doi:10.16854 / j.cnki.1000-0712.200424
    Abstract ( 767 )   PDF (1464KB) ( 105 )  
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    AC hysteresis loops of soft ferrite ring sample are measured under different

    conditions. It is found that the shape of the hysteresis loops changes with the amplitude and

    frequency of AC magnetic field strength. The changes of the shape of the AC hysteresis loops are

    caused by the waveform distortion of magnetic field intensity H. In a weak AC magnetic

    field,when magnetic induction intensity B is changed sinusoidally,the magnetic field

    intensity H is also changed sinusoidally. At this time,the shape of the hysteresis loop is

    elliptical. When the mag-netic field intensity increases,H-t curves show different degrees of distortion. The

    stronger the magnetic field is, the more severe the distortion of H - t curves is. At

    this time,the shape of hysteresis loops becomes bended and sharp,shows a fat“S”shape. These

    changes in the shape of hysteresis loops are explained through theoretical anal-ysis and experimental fitting.

    Discussion on the decomposition of ship induced magnetism and magnetic fields in oblique courses
    GUO Cheng-bao, HU Song, WANG Wen-jing, YIN Qi-qi
    College Physics. 2021, 40(6):  48.  doi:10.16854 / j.cnki.1000-0712.200341
    Abstract ( 444 )   PDF (1464KB) ( 160 )  
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    The decomposition of ship induced magnetism and magnetic fields in oblique

    courses is a difficult point in ship magnetic field analysis. The method based on the special

    situation of the magnetic signature at the typi- cal measurement points under the keel of ship can

    solve this problem easily and clearly. According to the magnetic field measurements in two

    headings of 180° difference,the sum of the longitudinal and the transverse magnetism of the ship

    can be separated. At the typical measurement points under the keel of a ship,the longitudinal and

    vertical components of the magnetic fields of the sum of the longitudinal and the transverse

    magnetism of the ship come from the longitudinal induced magnetism,and the transverse component of

    the magnetic fields comes from the transverse induced magnetism. Finally,the decomposition of ship

    induced magnetism and magnetic fields in oblique courses is realized.

    Thoughts on the ideological and political construction of electrodynamics course
    WANG Zhen-lin
    College Physics. 2021, 40(6):  53.  doi:10.16854 /j.cnki.1000-0712.210010
    Abstract ( 867 )   PDF (1283KB) ( 511 )  
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     In this paper,it is illustrated the facts that scientific development benefits from an innovation culture

    of society and the original innovation makes great impact on science and technology,and promotes social development

    from the perspective of the history of electrodynamics. Furthermore,it is demonstrated that the rich ideological

    and political connotations of electrodynamics,including the spirit of science in exploring nature and the value

    orientation of serving the society. Centering on !imparting knowledge,preaching truth,dispelling doubts,and fostering

    virtue',the thoughts and observations on the ideological and political connotations of this course were shared in

    this paper.

    Study of combining ideological and political education with Peer Instruction in college physics experiment
    CHEN Jun, ZHU Dao-yun, PANG Wei, WU Xiao, TANG Liang
    College Physics. 2021, 40(6):  57.  doi:10.16854 /j.cnki.1000-0712.200371
    Abstract ( 560 )   PDF (835KB) ( 177 )  
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    It is a difficult task to integrate ideological and political education into college physics experiment

    course because of the particularity of experimental teaching. In this paper,the ideological and political education

    combined with Peer Instruction method is applied to college physics experiment course innovatively. As a result,the

    students' interest and learning effect can be greatly enhanced by changing the traditional instillation teaching into

    autonomous discussion learning through this new teaching method. The core values of socialism run through the

    whole teaching naturally so as to achieve the goal of moistening things in silence.

    Practices of teaching mode reform on“Computational Materials Science”
    ZHANG Peng
    College Physics. 2021, 40(6):  62.  doi:10.16854 /j.cnki.1000-0712.210007
    Abstract ( 530 )   PDF (852KB) ( 64 )  
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    An innovative country is based on innovative talents. How to realize this goal by a basic subject

    course? Herein,we propose a Practice -Theory -Innovation ( PTI) teaching model of professional curse. In this

    model,students do practices first to experience the applications of theory. Then,they will seek answers from theoretical

    study. When they come back to research,they will make innovative achievements. Thus,this model focus on

    not only the form and contents of classroom teaching,but also out-of-class research activities. Since 2017,the executing

    of PTI model has led to remarkable improvement,resulting in fourteen SCI papers of undegraduate students.

    It has been found that the student's innovation capacity can be improved by combining in-class lecturing and outof-

    class activities.

    Exploration and integration of ideological and political elements in college physics teaching
    ZHU Xian-zhong, CHEN Fei-ming, FENG Cun-fang
    College Physics. 2021, 40(6):  66.  doi:10.16854 /j.cnki.1000-0712.200423
    Abstract ( 651 )   PDF (805KB) ( 349 )  
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    How to excavate ideological and political education ( IPE) resources which richly containe in college

    physics and to exert them on students in an imperceptible way,is an urgent problem for physics teachers to solve.

    According to the content of college physics course,the content system of IPE with its structural relationship is

    combed in this paper,which embodes the political and epochal features. Two searching methods of IPE materials

    are provided,and the educational function of the same important IPE materials in the knowledge system of physics

    is analyzed in order to provide basic ideas for constructing IPE material resources. Some methods of integrating the

    elements of IPE in the process of teaching implementation are discussed so as to provide support for the implementation

    of recessive teaching strategy.

    Research on the critical parameter of Faraday pattern generation under higher-frequency driving
    YAN Han, WANG Wei, ZHOU Lu-qun
    College Physics. 2021, 40(6):  71.  doi:10.16854 /j.cnki.1000-0712.200520
    Abstract ( 454 )   PDF (1054KB) ( 111 )  
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     In this experiment,the formation of Faraday pattern in xanthan gum solution driven by high frequency

    periodic external force is studied.The experimental results show that the critical parameter of pattern generation,

    the maximum driving acceleration,has a quasi linear relationship with the driving frequency.Further semiquantitative

    theoretical analysis shows that this result may be related to the balance of the energy dissipation caused

    by viscosity and the energy input of the external driving force,and the maximum velocity of solution surface may be

    the key characteristic quantity affecting the pattern generation.

    Theoretical analysis and visualization research on uniformity distribution of magnetic field in a finite solenoid
    ZHOU Xiao-yan, LIU Shi-kun, ZHANG Shu-tian, SUN Min, LU Jian, HUANG De-cai
    College Physics. 2021, 40(6):  76.  doi:10.16854 /j.cnki.1000-0712.200496
    Abstract ( 631 )   PDF (1533KB) ( 202 )  
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    The magnetic field of solenoid with length L = 200 mm is discussed in detailby using the Biot-Savart

    law and the principle of vector superposition.The magnetic fieldof a single current-carrying circular coil is exactly

    derived. Pythonis adopted to integrate the analytical expressions and visualize the corresponding magnetic induction

    line. Compared to the classical physics textbooks,both the theoretical derivations and the numerical solutionsare

    verifiedvalidly. Then the same analysis are carried out on both the magneticfield and the visualization of magnetic

    induction line of a finite current-carrying solenoid. The influence of coildensity and solenoid length on the uniformity

    of magnetic field are discussed in detail. It is found that the magnetic field is regarded as uniformity in the range

    of -74 mm ≤ z ≤ 74 mm of a solenoid when the density is greater than 1000 m-1 . The results in this paper provide

    intuitive and clear teaching materials for theoretical and experimental teaching in College Physics.

    Quantitatively dmonstration of principle of polarized light iterference in the experiment of crystal electro-optic effect
    DU Bo-hao, LIN Xing-yu, WANG jing
    College Physics. 2021, 40(6):  82.  doi:10.16854 /j.cnki.1000-0712.190574
    Abstract ( 418 )   PDF (1128KB) ( 150 )  
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    The principle of polarized light interference is quantitatively demonstrated using experiment of

    crystal electro-optic effect. With the help of index ellipsoid and small angle approximation,it is summarized that

    inherent order of stripe under convergent incident light is depended on position of stripe and driving voltage loaded

    on crystal. Extracting data from interference fringes,the linear relationship between the interference order and the

    square of the dark pattern position is verified,in different driving voltages,the correlation coefficients are all higher

    than 0.99; the electro-optic coefficient of crystal is measured by using the relationship between driving voltage and

    interference order,the error of the result is about 1.45% compared to accepted method. The experimental design

    can deepen the understanding of the theoretical knowledge of polarized light interference for junior undergraduates

    and enrich the experimental content.