Top Read Articles

    Published in last 1 year |  In last 2 years |  In last 3 years |  All
    Please wait a minute...
    For Selected: Toggle Thumbnails
    Home experiment: fractal geometry of crumpled paper ball
    LUO Jie, QIAN Jun
    College Physics    2021, 40 (10): 73-.   DOI: 10.16854 / j.cnki.1000-0712.200522
    Abstract1555)      PDF(pc) (267KB)(795)       Save
    During the pandemic period,experiments in home are set up in basic physics

    experiment course. Because of the simple preparation and easy measurement,the hand-crumpled

    paper ball experiment is chosen by many students. In this paper the fractal in the

    experiment of crumpled paper balls is discussed. The definition of fractal dimension is

    introduced to describe the internal irregularity of the crumpled paper balls. The fractal

    dimen- sion of normal A4 printing paper is measured experimentally and the influence of different

    paper hardness and paper layers on the fractal dimension of paper ball is studied.

    Related Articles | Metrics
    Electrodynamic explanation of faraday magneto-optical rotation effect
    XIAO Tian-ning, WANG Shuan-hu
    College Physics    2021, 40 (9): 72-.   DOI: 10.16854 / j.cnki.1000- 0712.210068
    Abstract1077)      PDF(pc) (463KB)(267)       Save
    Faraday magneto-optical rotation effect is a phenomenon that applying an external

    magnetic field to an isotropic medium will induce the optical rotation property. In this

    paper, light is regarded as an electromagnetic wave. By using the method of electrodynamics,

    starting from the equation of motion of electrons in an isotropic me- dium under an external

    magnetic field, the change of the system caused by the magnetic field will be analyzed. And then

    the relative dielectric tensor is obtained, which is solved by combining with Maxwell

    equations. By using the simple knowledge of electrodynamics, we can strictly deduce that the

    eigenstates of magneto-optical system must be right-handed and left-handed polarization.

    Furthermore, we can make readers better understand the source of fara-

    day effect in the perspective of eigenvalue problem.

    Related Articles | Metrics
    Dirac δ-function and its related applications
    ZHENG Shen-zhou, KANG Xiu-ying
    College Physics    2021, 40 (7): 25-.   DOI: 10.16854 /j.cnki.1000-0712.200456
    Abstract1061)      PDF(pc) (299KB)(354)       Save
    It is indicated that Dirac δ-function is a continuation of the discrete Kronecker

    δ-function,which plays an important role in both mathematics and physics. In this paper,the precise

    definition of Dirac δ-function is introduced based on the concept of generalized functions,and it

    is proved that the Dirac δ-function is not a usual function in the Lebesgue sense of local

    integrable one. To this end,the Dirac δ-function is here approximated in the sense of weak limit by

    making use of the sequences of the unit rectangle impulse functions,Gauss functions,Bell-

    shaped functions and Sinc-functions,respectively. In addition,it is checked that the Dirac

    δ-function is obtained as a generalized derivative of the Heaviside function,and its higher derivative is also shown.

    Moreover,the convo- lutions,scales,compound transformations,orthogonality and Comb Dirac functions are recalled,respectively. Fi- nally,the relationship between Dirac δ-function and generalized Fourier transform is introduced,and we present an application to solve the Dirichlet boundary value problem of the Poisson equation.

    Related Articles | Metrics
    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
    Abstract853)      PDF(pc) (616KB)(271)       Save
    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.

    Related Articles | Metrics
    vibration law of Wilberforce pendulum
    JIANG Fu-jin¹, HAN Can²
    College Physics    2021, 40 (11): 15-.   DOI: 10.16854 / j.cnki.1000-0712.210083
    Abstract780)      PDF(pc) (685KB)(582)       Save

    In this paper,a possible vibration model is conjectured according to the vibration

    characteristics of Wilberforce pendulum. Based on this model,the dynamic differential equations of

    Wilberforce pendulum are written out. Then the normal frequency and the analytical solution of the

    vibration are obtained. Finally,the numerical sim- ulation of the analytical solution is carried

    out and compared with the experimental data,which proves the rationali- ty of the conjecture

    Related Articles | Metrics
    Spherically averaging function and deduction of its differential equation
    CAI Jun, LI Min, WANG Qun
    College Physics    2021, 40 (8): 16-.   DOI: 10.16854 / j.cnki.1000-0712.210016
    Abstract764)      PDF(pc) (187KB)(291)       Save
    The initial- value problem of the wave equation in the three-dimensional case

    is a very important content in the course of methods of mathematical physics. In this paper,we

    discuss the definition of the spherically

    averaging function and how to build up the partial differential equation satisfied when we use the

    method of spherical means to solve this problem. A more concise procedure to deduce the

    equation of spherically averaging function is provided based on the analysis of the

    deduction appeared in the textbooks. Our discussion will clarify the basic meaning of the

    spherically averaged function and is benefit to the teaching and studying of the method of

    spherical means and other solutions to the equations of mathematical physics in three-dimensional

    spherical coordinates.

    Related Articles | Metrics
    Influence of spectrometer adjustment on the measurement of apex angle and minimum   deviation angle of a triangular prism
    LI Xin-jing, SONG Xin-bing
    College Physics    2021, 40 (8): 72-.   DOI: 10.16854 / j.cnki.1000-0712.200448
    Abstract734)      PDF(pc) (459KB)(264)       Save
    In the experiment of measuring the refractive index of a prism with a

    spectrophotometer,a key step is to adjust the object stage so that its main axis is perpendicular

    to the optical axes of the telescope and the collima- tor,which is called the standard case. It is

    analyzed that the influence on the measurement of apex angle and mini- mum deviation angle

    theoretically and experimentally when there is a deviation of the object stage. The experiments are

    performed for two cases. One case is that,in the telescope,it can be found that a green

    cross image reflectes from at least one surface of the double face plane mirror. In this case,the

    deviation is marked by recording the posi- tion of the green cross image. The other case is that

    the deviation of the object stage is measured with an extra sys- tem. In this case,the deviation

    degree of the object stage can be recorded directly. In experiment,the variation of the apex angle

    and minimum deviation angle of the prism with the deviation of the object stage is measured

    in the two cases. And the object stage’s deviation range,at which the experimental

    results has smaller deviations than standard measurement errors,is determined.

    Related Articles | Metrics
    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
    Abstract710)      PDF(pc) (1283KB)(490)       Save

     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.

    Related Articles | Metrics
    Superconducting quantum bits
    SU Fei-fan¹, YANG Zhao-hua¹, ², FAN Heng¹, ², ZHAO Shi-ping¹, ²
    College Physics    2021, 40 (7): 1-.   DOI: 10.16854 /j.cnki.1000-0712.210045
    Abstract664)      PDF(pc) (482KB)(424)       Save
    With Google's successful demonstration of " quantum supremacy" in 2019,the research of

    supercon- ducting quantum computing is attracting more and more attention around the globe.

    Superconducting quantum bits ( qubits) are macroscopic devices with fundamental quantum

    properties such as energy-level quantization,quantum- state superposition and quantum-state

    entanglement. They provide an excellent platform for the studies in many fields such as

    quantum physics,atomic physics,quantum optics,quantum chemistry,quantum simulation,quantum

    computing,and so on. In this article,we discuss the basic principles and structures of the

    superconducting phase-, charge-,transmon-,and flux-type qubits,as well as their device

    design and fabrication process. We also present a brief introduction to the rich research

    areas based upon the superconducting qubit architecture.

    Related Articles | Metrics
    Design experiment of university physics: research on demonstration device of Lissajous graphic
    WU Han¹, YU Yao¹, YOU Yin-tao¹, TANG Yong-jun¹, ZHANG Jin-long²
    College Physics    2021, 40 (10): 36-.   DOI: 10.16854 / j.cnki.1000-0712.210147
    Abstract658)      PDF(pc) (276KB)(262)       Save
    In this paper,a comprehensive design experiment of university physics,the self-making

    Lissajous graphic demonstration device is introduced. The reason why Lissajous figures is formed

    through theoretically analy- zing the thin film ' s forced vibration. The experimental

    results show that the shape and size of Lissajous figures change periodically when the

    frequency of the sound source increases. Finally,the effective surface tension value is estimated

    to be about 46.00 N / m through the measured resonance frequency when the surface area of latex

    ballon is twice the normal area,indicating that the device has certain practical applicability.

    Related Articles | Metrics
    Dynamic analysis of dancing coin
    HU Li
    College Physics    2021, 40 (7): 75-.   DOI: 10.16854 / j.cnki.1000-0712.200366
    Abstract650)      PDF(pc) (244KB)(729)       Save
    From the perspective of dynamics,this paper conducts a theoretical analysis on the third

    problem of the 2018 International Young Physicists’Tournament ( IYPT2018) ,“Dancing Coin”,and

    obtains the change in the height of the coin over time during a single beating. At the

    same time,the concept of “place error”is pro- posed,and the influence of coin place error

    on the coin’s tilting height is further discussed. It is found that the greater the

    place error,the faster the coin will rotate and the greater the maximum height of the

    coin will be reached. In the experiment,the process of coin dancing under different place

    errors was recorded with a high-speed camera,and software tracker was used to track. The

    comparison between the experimental results and the theoretical model verifies the

    correctness of the theoretical model.

    Related Articles | Metrics
    Green functions and their applications to ordinary differential equations
    QIAN Guang-yao, YAN Ruo-kun, WANG Ze-xi, ZHENG Shen-zhou
    College Physics    2021, 40 (9): 81-.   DOI: 10.16854 / j.cnki.1000- 0712.210142
    Abstract614)      PDF(pc) (460KB)(243)       Save
    In this paper, we are devoted to a review of the Green functions and the Green

      function method for solving the initial and boundary value problems of various ordinary

      differential equations. For the initial value prob- lem of linear ordinary differential equation

      of first order, the formula of Green function and the solution represented

      by Green function are given. For the boundary value problem and initial value problem of linear

      ordinary differential equation of second order, the calculation of Green function and the

      solution represented by Green function are shown, respectively. The calculation of Green

      function and the solution representation by Green function for Sturm-

      Liouville problem satisfying general initial value conditions are established. For the

      un-mixed and mixed boundary value problems of linear ordinary differential equations of second

      order, we also consider how to find Green function and the solution represented by Green

      function, respectively. Finally, For the boundary value problem of higher or- der linear ordinary

      differential equations, the Green function and the solution expressed by Green function

      are ob-

      tained.

    Related Articles | Metrics
    A new data processing method for Newton ring interference experiment
    HUA Xiao-bin, HUA Shi-qun
    College Physics    2021, 40 (7): 35-.   DOI: 10.16854 / j.cnki.1000-0712.200471
    Abstract607)      PDF(pc) (213KB)(195)       Save
    Based on Newton’s ring interference experiment,the air layer thickness difference

    in the vertical direction between two adjacent interference rings is half wavelength. By

    taking the diameters of interference rings measured by moving reading microscope as

    horizontal coordinates,and taking the air layer thickness differences de- termined by the order

    difference of interference rings as longitudinal coordinates,the large circle equation of

    the planoconvex lens sphere in Newton’s ring device can be fitted and used to obtain the

    curvature radius of the plano- convex lens sphere. The experimental results show that the

    new experimental data processing method needs less measuring points,the process is simple and

    the results are reliable.

    Related Articles | Metrics
    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
    Abstract600)      PDF(pc) (1464KB)(99)       Save
    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.

    Related Articles | Metrics
    Systematic error analysis of period of simple pendulum
    SHAO Yun
    College Physics    2022, 41 (1): 32-.   DOI: 10.16854 / j.cnki.1000-0712.210247
    Abstract591)      PDF(pc) (353KB)(146)       Save

    This paper analyzes and calculates the influence of the pendulum angle,the rotation of

    the ball,the mass of the suspension line,the air buoyancy and the air resistance on the period of

    the pendulum one by one. Tak- ing a 1 m length and 5° swing angle small amplitude pendulum as an

    example,the relative errors of the five factors are

    +0.45‰,+0.02‰,-0.45‰,+0.07‰,-0.14‰,respectively,and the total is only -0.05‰,which means that the

    five error factors almost cancel each other,and the systematic error of the small

    pendulum experiment is very small in theory. This paper gives a more detailed

    reasoning,calculation and analysis process,especially the reasoning process of air resistance

    moment,as well as charts and tables,for providing a more complete and accu- rate

    understanding. Finally,some necessary explanations are given in view of some possible deficiencies

    in people's understanding of air resistance.

    Related Articles | Metrics
    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
    Abstract556)      PDF(pc) (1079KB)(226)       Save
    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.

    Related Articles | Metrics
    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
    Abstract554)      PDF(pc) (805KB)(338)       Save

    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.

    Related Articles | Metrics
    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
    Abstract552)      PDF(pc) (764KB)(224)       Save
    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.
    Related Articles | Metrics
    Study on the Ampere circuital theorem in stationary magnetic fields
    HU Xi-kui, LI Li, FENG Chun-bao, MOU Qiong
    College Physics    2021, 40 (8): 20-.   DOI: 10.16854 / j.cnki.1000-0712.200523
    Abstract547)      PDF(pc) (267KB)(274)       Save
    The Ampere circuital theorem is an important law in stationary magnetic fields and is

    often used to analyze the magnetic flux intensity of a current system with a certain symmetry. The

    useful conditions of the Ampere circuital theorem and its mathematical principles are studied. The

    misunderstanding that the Ampere circuital theo- rem is incorrect in a finite-length

    current-carrying straight wire system is clarified through a simple model. The uni- versality of

    the Ampere circuital theorem is exemplified. It helps students to master Ampere circuital

    theorem and understand the properties of magnetic fields.

    Related Articles | Metrics
    A new definition of Lie derivative
    HE Xiao-kai¹, CAO Zhou-jian²
    College Physics    2021, 40 (7): 8-.   DOI: 10.16854 / j.cnki.1000-0712.210091
    Abstract540)      PDF(pc) (160KB)(213)       Save
    Lie derivative is an important concept of differential geometry. It is widely used in

    mathematics and physics. The Lie derivative is defined through the push-forward and pull-back

    maps. In this paper,a new definition of Lie derivative is presented. Instead of the abstract

    maps,we firstly introduce the concept of an adapted coordinate

    system of a smooth vector field on a manifold. Then a new definition of Lie derivative is given

    based on an adapted coordinate. It can be shown easily that the new definition is independent of

    the specific choice of an adapted coordi-nate system. After that,we deduce the explicit expression of the Lie derivative in general

    coordinate system,which admits the same form as the Lie derivative definition in usual textbooks. Compared to the

    existing definition of Lie derivative in usual textbooks,our new definition is much easier for

    beginners to understand.

    Related Articles | Metrics
    Notes on the principles of quantum mechanics
    YANG Shi-jie
    College Physics    2021, 40 (11): 1-.   DOI: 10.16854 / j.cnki.1000-0712.210122
    Abstract537)      PDF(pc) (244KB)(443)       Save
    The principles of quantum mechanics as well as basic concepts and classical

    correspondence are re- examined from advanced point of views. We also discusse the relation

    between Planck constant and representation transformation.

    Related Articles | Metrics
    Design and practice of ideological and political education in the teaching of electromagnetic field and electromagnetic wave
    SONG Ling-ling, HUANG Wen
    College Physics    2021, 40 (11): 36-.   DOI: 10.16854 / j.cnki.1000-0712.210201
    Abstract532)      PDF(pc) (448KB)(437)       Save
    Based on Gauss theorem in electromagnetic field and electromagnetic wave,in this paper

    the design of teaching with teachers as the main body is carried out,in which there are five

    teaching links: introduction,es- tablishment,breaking,extension and conclusion,so as to realize

    the teaching conception of knowledge inheritance and ability migration. Integrating the ideological

    and political elements into the curriculum from three dimensions not only solve the teaching

    difficulties,such as determining the size of the spatial angle,the key meaning of

    positive and negative,and the calculation of the spatial angle of closed surface,but also guide

    students to see problems from multiple perspectives,and help students to establish a correct

    outlook on life,values,and the world,so as to real- ize the goal of condensing the knowledge in the

    value dissemination and realizing value guidance in the knowledge dissemination.

    Related Articles | Metrics
    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
    Abstract527)      PDF(pc) (885KB)(213)       Save
    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.

    Related Articles | Metrics
    Three-dimensional simulation and visualization of the motion of rigid body and discussion on physical pendulum related problems
    LIN Jiong-hui¹, LIU Yu-ying², SONG Min²
    College Physics    2021, 40 (7): 68-.   DOI: 10.16854 / j.cnki.1000-0712.200404
    Abstract526)      PDF(pc) (710KB)(247)       Save
    In this paper,the rotational motion of rigid body around a fixed axis is studied by

    using Newton’s second law for rotation and in angular form with VPython software. Some

    special examples discussed in detail are motions of rotating uniformly rod under different

    torques,the path,angular displacement,angular velocity and mov- ing process,and were visualized

    intuitively in real time. The conservation of the energy of rotating rigid rod only ex- perienced

    with torque of gravity can be verified by VPython software. The plane motion of rigid

    body ( translation plus rotation) and vibration of rigid body are also studied. Especially,the

    chaos state of rigid rod with large rotating angle is investigated. The simulation deepens the

    understanding of textbook knowledge.

    Related Articles | Metrics
    Thermodynamics and geometry
    LIU Quan-hui
    College Physics    2021, 40 (8): 1-.   DOI: 10.16854 / j.cnki.1000-0712.210029
    Abstract524)      PDF(pc) (244KB)(663)       Save
    The interesting connections between thermodynamics and geometry have all but

    vanished from the literature.Three thermodynamic issues are treated with geometry.The first is

    how to geometrically interpret the Thom- sen-Berthelot principle,leading to the third law of

    thermodynamics.The second is why the van der Waals parame- ters a and b depend on the temperature

    once the equation of state is viewed as a two-dimensional surface.The third is that the

    thermodynamic fluctuations permit metric representations associated with the Riemann geometry,and

    the van der Waals equation of state is used to demonstrate the scalar curvature measures the

    interactions.Attempts to un- derstand the thermodynamics within geometry do not only offer an

    effective teaching and learning,but also may be helpful to find new research areas.

    Related Articles | Metrics
    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
    Abstract511)      PDF(pc) (1533KB)(166)       Save

    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.

    Related Articles | Metrics
    Solutions for a familiar mechanical problem
    SU Guo-zhen
    College Physics    2021, 40 (6): 5-.   DOI: 10.16854 / j.cnki.1000-0712.200346
    Abstract509)      PDF(pc) (861KB)(406)       Save
    New solutions for a mechanical problem relating to the harmonic oscillation are presented based on a deep analysis.
    Related Articles | Metrics
    A brief analysis of the method for constructing the structures of twisted graphene bilayers
    CHEN Ming-xing
    College Physics    2021, 40 (8): 8-.   DOI: 10.16854 / j.cnki.1000-0712.210060
    Abstract495)      PDF(pc) (381KB)(290)       Save
    Twisted graphene bilayer has been a hot topic in condensed matter physics.Here,a method

    for con- structing the geometric structure of graphene supercells is illustrated,which makes use of

    the translational symmetry of crystal and the transformation matrix between the supercell and the

    primitive cell. Then,the method is applied to construct the structure of twisted graphene bilayers.

    This system can be used as an example in the lecture of solid state physics,which is

    helpful for students to achieve a better understanding of the mathmatic method of describing the

    geometric structure of crystals.

    Related Articles | Metrics
    Further study on vector properties of angular displacement
    WANG Jing-zhou
    College Physics    2021, 40 (7): 12-.   DOI: 10.16854 / j.cnki.1000-0712.200488
    Abstract494)      PDF(pc) (244KB)(223)       Save
    Discussion on vector properties of angular physical quantity,through graphic

    comparison,or through formula calculation,many papers draw the conclusion that infinitesimal

    rotation is vector and finite rotation is not vector.Neither point out the physical

    fundamental reason. According to the invariance of physical quantity and the covariance of

    transformation,it is proved that the rotation vector is not true vector,that of the essential

    reason is the levorotation and dextrorotation of the coordinate system.

    Related Articles | Metrics
    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
    Abstract493)      PDF(pc) (876KB)(151)       Save
    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.

    Related Articles | Metrics
    Diffraction and splitting function of phase grating
    ZOU Yi-yun, LIN Jia-li, LU Yue-yuan, YAN Xiao-na
    College Physics    2021, 40 (11): 64-.   DOI: 10.16854 / j.cnki.1000-0712.210104
    Abstract490)      PDF(pc) (407KB)(125)       Save
    Using the coherent superposition,diffractions are deduced when a plane wave incidents on

    a phase grating. Results show that the ±1 order diffraction of the phase grating can get the

    maximum intensity and realize the splitting function,overcoming the problems in amplitude grating

    where the 0 order diffraction has the maximum in- tensity but with no splitting function. The

    diffraction efficiency of ±1 order diffraction with respect to the duty ratio and phase introduced

    by the phase material are discussed. The method we provided here has implicit physical mean- ings

    and is easy to adapt to other diffraction structure.

    Related Articles | Metrics
    Theoretical models and an imaging experiment of the laser speckle drift phenomenon
    GUO You-xi, HE Yun-bo, LIU Rong-zhen, GONG Dian-jin-feng, XIA Cheng-jie
    College Physics    2021, 40 (7): 78-.   DOI: 10.16854 / j.cnki.1000-0712.200524
    Abstract487)      PDF(pc) (511KB)(283)       Save
    A numerical method of calculating objective and subjective laser speckle

    patterns are developed based on the principles of Fourier optics. Expressions for the drift

    velocities of laser speckle and light spot in a sub- jective pattern are derived based on

    geometrical optical principles. Devices of imaging experiments are set up to ob- serve the

    objective and subjective laser speckle patterns and their respective drift phenomena. Methods

    to quantify the drift velocities of speckles and spots are established based on image processing

    techniques,which combine cor- relation function,the Fast Fourier Transform algorithm and

    convolution theorem. Both experimental and numerical results match perfectly with our

    theoretical expressions,which validates the numerical method and geometrical opti- cal model. This

    work provides a systematic method to research and an intuitive way to understand the laser speckle

    drift phenomenon.

    Related Articles | Metrics
    Practical research on the application of mind map in university science courses teaching—taking the course “Introduction to laser technology”as an example
    LI Hong-yu¹, XU Lin-xin², Hou Dan¹
    College Physics    2021, 40 (7): 55-.   DOI: 10.16854 / j.cnki.1000-0712.200458
    Abstract474)      PDF(pc) (467KB)(122)       Save
    Through tutoring students to preview,arranging homework and collecting feedback

    in teaching the course of introduction to laser technology,the teacher let students freely choose

    whether to use mind map or not to complete homework and gradually guided students to try to use

    it to summarize knowledge points. These measures stimulated students’interest in applying

    mind map as a learning tool,and also made students’enthusiasm improved in learning the course of

    introduction to laser technology. It is also found that the mode of mind map plus notes not only

    took advantages of mind map to help clarify knowledge context,but also remedied the shortcomings

    that mind map could not show the specific content of knowledge points with notes.

    Therefore,this mode is more suitable for the study of physics subjects when compared with the

    simple mind map mode.

    Related Articles | Metrics
    Development and application of physical animation based on HTML5 technology
    SONG Hong-xiao¹, ZHANG Qi-wei², LIU Jian-qiang¹
    College Physics    2021, 40 (7): 51-.   DOI: 10.16854 / j.cnki.1000-0712.210005
    Abstract468)      PDF(pc) (309KB)(104)       Save
    With mobile devices such as mobile phones replaced computers as the mainstream

    way of surfing the internet,the Flash animation that is currently used in college physics online

    learning,is required to be migrated to mobile devices in order to meet the needs of using mobile

    devices for learning. HTML5( H5 for short) is currently the best substitution of Flash. Based

    on the design and development practice of H5 animation in the new physics textbooks,in

    this article,the design ideas and development steps of physics h5 animation is summarized,the

    two steps of topic selection and physical modeling and interface and interactive function design in

    detail with examples is described.

    Related Articles | Metrics
    One way to explain Ampere's circuital theorem
    GENG Zhi-hao
    College Physics    2021, 40 (7): 17-.   DOI: 10.16854 / j.cnki.1000-0712.200446
    Abstract464)      PDF(pc) (271KB)(322)       Save
    A new distinct and concise method to demonstrate the Ampere’s circuital theorem

    is proposed for general physics course of non-physics majors.It is practibal to enhance

    students’comprehension of this theorem.

    Related Articles | Metrics
    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
    Abstract463)      PDF(pc) (835KB)(146)       Save

    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.

    Related Articles | Metrics
    Classical and quantum statistical distributions of harmonic oscillators
    KANG Lin-hui, ZHANG Lin
    College Physics    2021, 40 (7): 30-.   DOI: 10.16854 / j.cnki.1000-0712.200508
    Abstract455)      PDF(pc) (359KB)(259)       Save
    There are some differences and connections between classical statistics and quantum

    statistics,and they can be converted to each other under certain conditions. The harmonic

    oscillator model is very important in physics,for example,the movement of the harmonic

    oscillator state description,energy,and the uncertainty princi- ple,spatial distribution and

    probability distribution of the two kinds of statistical methods are compared and summa-

    rized,respectively. The classical statistics of harmonic oscillator and the similarities and

    differences with quantum statistical distribution are deepened to the further understanding of

    quantum dynamics behavior and cognition.

    Related Articles | Metrics
    Application of measurement uncertainty analysis in university physics experiments — gravity acceleration measured by single-swing
    ZHANG Zhu li, CHEN Xin lei, LU Mei hong
    College Physics    2022, 41 (2): 31-.   DOI: 10.16854/j.cnki.1000-0712.200521
    Abstract453)      PDF(pc) (826KB)(116)       Save
    Gravity acceleration is an important mechanical constant in physics. There are many methods to measure the value of gravity acceleration, and the simple pendulum method is often used in university physics experiments. However, the experimental principle only studies the motion of the single pendulum ball and ignores the influence of the size of pendulum, buoyancy, cycloid mass and other factors, so the measurement results are not accurate enough. The relative accurate formula of gravity acceleration and the corresponding synthetic standard uncertainty formula are obtained by correcting the system error that caused in the measurement of gravity acceleration by the simple pendulum method. Finally, the measured data are analyzed and calculated reasonably, and the more accurate experimental results are obtained.
    Related Articles | Metrics
    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
    Abstract448)      PDF(pc) (2511KB)(84)       Save
    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.

    Related Articles | Metrics
    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
    Abstract440)      PDF(pc) (852KB)(60)       Save

    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.

    Related Articles | Metrics
    Misunderstandings in the experiment of measuring acceleration of gravity with Kate   pendulum   ——— Taking virtual simulation experiment as an example
    SHENG Yan
    College Physics    2021, 40 (10): 32-.   DOI: 10.16854 / j.cnki.1000-0712.210066
    Abstract439)      PDF(pc) (260KB)(143)       Save
    Kate pendulum is an accurate and ingenious experimental method to measure the

    acceleration of gravity. In this paper,based on the principle,the model of Kate pendulum is

    introduced,the experimental method is summed up,some common experimental errors are pointed out,and

    the analysis is given so as to guide the ex- perimenters to pay attention to understand the

    experimental principles and avoids going into the experimental errors.

    Related Articles | Metrics
    Demonstration instrument for vacuum measurement
    WU Yuan, GUO Chao-xiu, YIN Ya-ling, CHEN Li-qing
    College Physics    2021, 40 (7): 38-.   DOI: 10.16854 / j.cnki.1000-0712.200380
    Abstract432)      PDF(pc) (293KB)(135)       Save
    The difference between quantum mechanics and classical physics is that the energy of the

    vacuum is not zero. Normally,due to the small energy,it is hard to measure the vacuum field

    directly only when the quantum measurement,such as homodyne detection,is used. Meanwhile,there is

    a lack of the experimental demonstration based on quantum measurement in college physics,which

    makes the theory of quantum mechanics hard to be un- derstanded. In this paper,a

    demonstration instrument for vacuum measurement based on homodyne detection is pro- posed. This

    instrument is simple in principle,intuitive in phenomenon,easy to operate and maintain. It makes

    up for the blank of quantum mechanics experiment in college physics,which realizes the expansion of

    frontier physics in college physics teaching.

    Related Articles | Metrics
    How much charges on a hemisphere?
    QIU Wei-gang
    College Physics    2021, 40 (9): 21-.   DOI: 10.16854 / j.cnki.1000- 0712.200546
    Abstract431)      PDF(pc) (449KB)(227)       Save
    The electric potential produced by two hemispheres with constant and opposite potential

    is expressed as infinite sums of Legendre functions in spherical coordinate. The electric charge density and total charges on the

    hemisphere are derived. Calculation shows that the charge is infinite.

    Related Articles | Metrics
    Electrostatic induction of the infinite ungrounded conductor plate
    FU Quan-hong, ZHENG Jian-bang, FAN Yuan-cheng, ZHANG Fu-li
    College Physics    2021, 40 (11): 5-.   DOI: 10.16854 / j.cnki.1000-0712.210041
    Abstract429)      PDF(pc) (239KB)(301)       Save
    Utilizing the uniqueness theorem of the boundary value problem of electrostatic field,we

    strictly an- alyze the problem of electrostatic induction of the infinite ungrounded conductor

    plate,and use the simulation soft- ware of COMSOL Multiphysics to verify the theoretically

    calculated results.

    Related Articles | Metrics
    Quantum speed limit time
    XU Kai, ZHANG Guo-feng
    College Physics    2021, 40 (10): 1-.   DOI: 10.16854 / j.cnki.1000-0712.210015
    Abstract424)      PDF(pc) (174KB)(382)       Save
    The minimum time required for the system to evolve from the initial state to the target

    state is defined as the quantum speed limit time. This concept can be used to estimate the maximum

    rate of evolution from a given quantum state to a desired target state. Here,the development of

    quantum speed limit time from closed system to open system is reviewed,and the influence of

    non-Markovian environment on the quantum speed limit time of open system is discussed. We hope

    that our review is helpful for the future study of the quantum speed limit time.

    Related Articles | Metrics
    Application of charge projection method in the study of charge distribution law of infinitely long conductor thin plate
    ZHOU Qun-yi¹, MO Yun-fei², ZHOU Li-li³, HOU Zhao-yang⁴
    College Physics    2021, 40 (7): 19-.   DOI: 10.16854 /j.cnki.1000-0712.200545
    Abstract423)      PDF(pc) (596KB)(180)       Save
    Using the charge distribution law of a uniformly charged cylinder of infinite

    length and the field strength formula of an infinitely long charged straight line,and adopting

    the charge projection method,the surface charge distribution of a charged conductor of finite

    width and infinite length has been deduced. According to the principle of electric

    potential superposition,the electric potential integral formula is derived; using the relationship

    between field strength and electric potential,the integral formula of the two components of

    electric field strength is derived. The formula is dimensionless,and the values of the components

    of electric potential and field strength are calculated through numerical integration. The

    electric potential and field strength of the charged conductor sheet of finite width and infinite

    length are shown in the picture,and the two-dimensional equipotential lines and electric

    field lines are also drawn in the diagram,which fully shows the distribution law of field strength.

    Related Articles | Metrics
    Superposition rule of refraction imaging of object points through multi-layer parallel   medium interface and several application analyses
    SHAO Yun
    College Physics    2021, 40 (8): 23-.   DOI: 10.16854 / j.cnki.1000-0712.200493
    Abstract423)      PDF(pc) (448KB)(70)       Save
    In this paper,a simple and natural reasoning method is used to deduce the virtual image

    point posi- tion of the secondary refraction imaging of object point refracting through the

    parallel medium interface,and the so- called “superposition rule of refraction imaging of object

    points through multi-layer parallel medium interface”is found. This paper discusses the

    coordinates of image points in several special cases: the refraction phenomenon of “body

    head separation”of the female swimmer in swimming pool is analyzed and explained; the imaging

    character- istics of objects in the air through glass blocks are analyzed,the optical basis

    for people to usually use thin glass windows is pointed out; the refraction imaging of an

    object point in air through a medium with linear refractive index change is studied in detail,and

    it is pointed out that the position of the imaging point in the medium with uniformly varying

    refractive index is almost the same as that in the medium with uniform refractive index of

    same thickness, except for the large angle of view from 80° to 90°. The reasoning methods and

    conclusions in this paper may provide reference for the teaching and scientific research of related

    contents.

    Related Articles | Metrics
    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
    Abstract416)      PDF(pc) (805KB)(167)       Save
    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.

    Related Articles | Metrics
    The intuitional teaching method of the beat phenomenon
    XIA Zheng-rong, LI Rong-qing, TONG Yue, XU Xiao-xue
    College Physics    2021, 40 (9): 10-.   DOI: 10.16854 / j.cnki.1000- 0712.200324
    Abstract416)      PDF(pc) (534KB)(176)       Save
    Combining the rotating vector method, the constructed process of the beat phenomenon and

    the rea- son that caused the characteristic of the Beat phenomenon are analyzed. Then the

    amplitude and the phase position of the beat phenomenon are discussed in detail. Finally, the

    phase jump is also shown by the rotating vector method

    clearly. The method describing the beat phenomenon in this paper makes the model of the beat

    phenomenon so visu-al and intuitive that one can understand it very easily.

    Related Articles | Metrics
    Simple measurement of the axis distance and interpupillary distance
    ZHOU Si-ying¹, CHANG Kai-ge², MAO Sheng-chun², GAO Bo²
    College Physics    2021, 40 (12): 55-.   DOI: 10.16854 / j.cnki.1000-0712.210044
    Abstract415)      PDF(pc) (708KB)(67)       Save

    If the interpupillary distance does not match the axis distance of one's glasses,the

    scene would be deformed,distorted and blurred,and this could result in visual fatigue and

    irreversible damage to the eyes. In this paper a measurement scheme by using laser pen,ruler and

    mobile phone is proposed. By analyzing the principle of optical imaging,the measurement models of

    axis distance in four position cases of laser pen are established,and the calculation formulas of

    two glasses with the same or the different degrees are given. Then a platform is built to do ex-

    periment,and the factors affecting on the accuracy are analyzed. Tracker video analysis software is

    also used to fur- ther reduce the measuring error. Finally,through taking pictures by using mobile

    phone,the interpupillary distance is accurately measured. Thus conveniently measuring the

    interpupillary distance and the axis distance and accurately judging whether they match or not are

    realized.

    Related Articles | Metrics