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Table of Content

    07 January 2021 Volume 40 Issue 01
      
    Study of micro-vibrating by a double grating diffraction
    XIAO Guo-hong, ZHONG Xi-hua, LIU Ping
    College Physics. 2021, 40(01):  1-6.  doi:10.16854 /j.cnki.1000-0712.200283
    Abstract ( 1084 )   PDF (967KB) ( 510 )  
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    Based on cosine-style grating,the interference of diffraction by a double grating is studied theoretically with a wavefront phase-factors method. The patterns of Fraunhofer diffraction are shown by some formulas. Intensities’changing of each order diffraction is deduced as one grating translates along another horizontally and vertically. The intensities’changing figures are also shown by numerical simulation. These formulas form a foundation for experimental applications. One of these obvious applications is to measure the amplitude and the frequency of a harmonic micro-vibrating.
    Application of chemical potential to determine equilibrium concentration of Hydrogen on Tungsten surface
    LU Guang-hong, LI Yu-hao, ZHANG Xue-song, JIN Shuo, ZHOU Miao, CHENG Long
    College Physics. 2021, 40(01):  7-11.  doi:10.16854 /j.cnki.1000-0712.200136
    Abstract ( 1167 )   PDF (931KB) ( 433 )  
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    As an important physical quantity in Thermodynamics and Statistical Physics,chemical potential describes the trend of particle transition in thermodynamic systems.Here,by taking the case of“equilibrium concentration of hydrogen on tungsten surface”as an example,we introduce the concept of the chemical potential to determine equilibrium concentration.Careful analyses on the variation of the chemical potential for hdyrogen in both the molecular hydrogen system and tungsten surface system explicitly illustrate the equilibrium concentration of hydrogen on tungsten surface under different temperatures and pressures.Such equilibrium concentration calculation greatly benefits the understanding of the physical origin of chemical potential concept in Thermodynamics and Statistical Physics.
    Talking about“wandering earth”again———How much work does it take to make the earth out of the solar system?
    YU Feng-jun, TIAN Jun-long, TANG Zhen-jie, JU Lin
    College Physics. 2021, 40(01):  12-16.  doi:10.16854 /j.cnki.1000-0712.200049
    Abstract ( 1324 )   PDF (901KB) ( 746 )  
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    Starting from a grand plan of a domestic sci-fi blockbuster“The Wandering Earth”,the minimum mechanical work needed to take the earth out of the solar system is deduced and calculated by using the law of conservation of momentum,theorem of kinetic energy,and concept of escape velocity and effective recoil jet velocity. The result is 2.72×1032 J,and the possibility of separating the earth from the solar system is discussed from the perspective of energy.
    The series expressions of relations between period and amplitude and energy for nonlinear vibration
    HAO Ji-guang, HUANG Yi-bin
    College Physics. 2021, 40(01):  17-20.  doi:10.16854 /j.cnki.1000-0712.180157
    Abstract ( 883 )   PDF (828KB) ( 348 )  
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    The series expressions of relations between period and amplitude and energy are discussed for general one-dimensional nonlinear vibration,and solutions up to the fourth order are obtained. They are checked by the rigorous solution of two examples,i.e.,simple pendulum and central force.
    Variational-perturbation calculation of the first excited state energy levels for Helium atom
    BAI Zhan-wu, YAN Zhan-yuan
    College Physics. 2021, 40(01):  21-23.  doi:10.16854 /j.cnki.1000-0712.200022
    Abstract ( 1264 )   PDF (742KB) ( 2789 )  
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    The energies of 1S2S states of Helium atom are calculated by variational-perturbation method. The energies are calculated firstly by the variational method and then by the second-order perturbation theory. The results are superior to pure perturbation theory,and match well with the experimental data.
    Experimental system for chaotic circuit based on NI-myDAQ data acquisitor
    LIAO De-ju, SHEN Han, FENG Rao-hui, CUI Xin-tu, HUANG Zhen-cheng,
    College Physics. 2021, 40(01):  24-26.  doi:10.16854 /j.cnki.1000-0712.200252
    Abstract ( 995 )   PDF (1476KB) ( 154 )  
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    Chaotic circuit is a typical content of nonlinear system in the course of college physics experiment. In order to improve students' learning efficiency and self-learning ability of nonlinear experiment,a chaotic circuit experiment system is designed base on NI-myDAQ and LabVIEW. This system can improve the precision of small changes of chaotic parameters. It could intuitively display and record chaotic patterns in real time under different

    parameters,and save phase diagrams,time domain diagrams and data. The Chua's chaotic circuit is measured by using this system,and the experimental results under certain parameters are given and compared with the simulation results obtained by using Multisim. The experimental results are in well agreement with that of the simulation.

    Measuring gravitational acceleration and speed of sound by smartphones at home
    MIAO Hong-mei, YANG Zhi-min
    College Physics. 2021, 40(01):  33-37.  doi:10.16854 /j.cnki.1000-0712.200155
    Abstract ( 2915 )   PDF (1138KB) ( 899 )  
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    The experiment of Doppler effect is conducted with phyphox at home by employing two smartphones which acted as the sound source and the receiver,respectively. The sound source or the receiver fell freely so that the frequency and the velocity versus times can be obtained. The gravitational acceleration and the speed of sound can be calculated through data processing. Furthermore,the measured and theoretical values are compared. The reliability of Doppler effect experiment with smartphones is verified,and the results will provide some guidance for future experiments and data processing.
    Method and technology of testing the buried depth of conductors of substations’grounding grids
    LIU Yang, SUN Wen-jie, FU Xiao-dong
    College Physics. 2021, 40(01):  33-37.  doi:10.16854 /j.cnki.1000-0712.200171
    Abstract ( 615 )   PDF (1589KB) ( 218 )  
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    In order to get the reality buried depth of conductors of substation’grounding grids,an exciting current of a definite frequency is injected directly into grounding grid by two ground lead wires. Then,the surface magnetic induction intensities of different places are measured based on the electromagnetic induction theory. We can obtain the practical buried depth of grounding grids by information of the magnetic fields and the place of measuring point places. The feasibility of the testing method is analyzed and the injecting apparatus are designed and developed.The correctness of the method is verified by laboratory experiments and field tests in substation. The results of theory analysis and measuring show that the technology method is operated easily and the measuring results are accurate and reliable. It can be used in the engineering practice of transport inspection of grounding grids. It shows that the theory of physics and circuit can be used to engineering technology.

    Research on the program problem of the NMR pulse sequence design in quantum algorithm
    College Physics. 2021, 40(01):  38-47.  doi:10.16854 /j.cnki.1000-0712.200052
    Abstract ( 992 )   PDF (1481KB) ( 485 )  
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    Based on the physical model of two qubit NMR quantum processor,using the spin-1/2 algebra theory proposed by Raedt group,according to the definition of quantum controlled not gate and principle of Grover quantum algorithm,the design process of four different pulse sequences of quantum controlled not gate and two different pulse sequences of two qubit Grover quantum algorithm are introduced. The time-dependent Schrdinger equation is numerically calculated for simulating quantum controlled not gate and two-qubit Grover quantum algorithm, which is equivalent to executing quantum controlled not gate and two-qubit Grover quantum algorithm operations, we demonstrate and analyze the quantum programming problem of quantum controlled not gate and two-qubit Grover quantum algorithm nuclear magnetic resonance pulse sequence design.
    Practice and introspection on the online teaching of college physics
    LI Rui-shan, ZHANG Pei-zeng, FENG You-cai
    College Physics. 2021, 40(01):  48-50.  doi:10.16854 /j.cnki.1000-0712.200265
    Abstract ( 963 )   PDF (1211KB) ( 206 )  
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    Recently due to the impact of the pandemic,online teaching was adopted on a massive scale in colleges and universities across the country. In this paper,some experiences,including communication forms,advantages of online teaching,and ideological teaching etc,are concluded from the teaching practices of online college physics,and difference and connection between online teaching and classroom teaching are explored. Online teaching has become a parallel method or an auxiliary means of classroom teaching. In the long term,the in-depth thinking of the online teaching practice can provide valuable ideas for further improving the teaching effect of college physics.
    From solving problems to researching———case teaching in Computational Physics
    LU Ai-jiang
    College Physics. 2021, 40(01):  51-54.  doi:10.16854 /j.cnki.1000-0712.200248
    Abstract ( 932 )   PDF (1116KB) ( 239 )  
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    Case teaching is recommended in Computational Physics class in this paper. The advantages of online teaching make such a transformation of teaching mode realize. The old mode of lecture-problems solving-testing scheme should be replaced by the new mode of question-analyze-solution. The results can be obtained through modeling and researching. It provides an opportunity for students not only to apply the physics knowledge but also get a training in science research. It is meaningful for the ability enhancement of the undergraduates.
    Fano resonance excited in coupled spring oscillators driven by an external force
    ZHENG Zi-rui, LU Si-wei, LIAO Chen-hao, YANG Kun, GE Yu-hua,
    College Physics. 2021, 40(01):  55-59.  doi:10.16854 /j.cnki.1000-0712.200287
    Abstract ( 1508 )   PDF (1296KB) ( 649 )  
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    Fano resonance which features asymmetric resonant line shape is a general resonance phenomenon occurred in all kinds of physical systems. It originates from quantum physics and the corresponding microscopic image is the interference between a narrow discrete state with a broad continuous state in atomic spectra. In this paper, taking two coupled spring oscillators in classical mechanics as an example and one of the coupled spring oscillators is driven by a periodic external force,a Fano resonance phenomenon which occurred in quantum mechanics is successfully analogized in classical mechanics. By analyzing the dynamic equation of each oscillator and solving their vibration formula rigorously,the relationships between the amplitude and phase of each oscillator and the frequency of the external driving force are obtained. The results show that the oscillator driven by the external force in the coupled system can excite both asymmetric Fano resonance and symmetric Lorentz resonance,while the other oscillator can only excite Lorentz resonance. The derivation and analysis of this paper give readers a deeper understanding of the Fano resonance and its excitation conditions.
    Stars cannot be surpassed———The origin of three-body problem
    SHAO Han-yong
    College Physics. 2021, 40(01):  60-65.  doi:10.16854 /j.cnki.1000-0712.200077
    Abstract ( 1908 )   PDF (1915KB) ( 804 )  
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    Since Newton in the Mathematical Principles of Nature Philosophy for the first time to define three body problem,people have been working on this problem for 300 years. At first,Euler and Lagrange studied some relatively simple three -body system problems. Poincaré first considered the restricted three -body problem,but found that its trajectory is too complex to be described. He turned to prove that there is no analytical solution for the three-body problem,and created a new subject,nonlinear dynamics.
    On temperature dependence of the van der Waals a and b parameter
    ZHANG Zi-yi, LI Xin-yu, WANG Xin, LIU Quan-hui
    College Physics. 2021, 40(01):  66-69.  doi:10.16854 /j.cnki.1000-0712.200208
    Abstract ( 3171 )   PDF (1103KB) ( 1591 )  
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    On the problem whether the van der Waals parameters a and b depend on temperature,different literature

    gives different answer,and even the same literature in different pages gives contrary answer. In thermody

    namics,they are approximately treated as constants due to matching the thermodynamic coordinates of the critical

    point and van der Waals equation of state can be expressed as the corresponding state law. Once the parameters a

    and b depend on the temperature,the corresponding state law does not hold true,and other peculiarities of the van

    der Waals equation of state is lost accordingly. In statistical mechanics,we usually obtain a Virial expansion of the

    equation of state; once the van der Waals equation is used to interpolate to this expansion,they are temperaturedependent

    except some special cases. Therefore,the different statements on temperature dependence of the van der

    Waals a and b parameter in thermodynamics and statistical mechanics are in fact originates from implicit assumption

    of the same application domain of the van der Waals equation of state in two different disciplines.

    Electric field intensity on the central axis of three-dimensional point charge   system with fullerene lattice structure
    JIN Li-zhen, WU Xian-li, WANG Xing-le, CHEN Hao, XIE Jian-ping
    College Physics. 2021, 40(01):  70-74.  doi:10.16854 /j.cnki.1000-0712.200280
    Abstract ( 838 )   PDF (1100KB) ( 261 )  
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    Based on the principle of superposition,the distribution of electric field intensity on the central axis

    of the three-dimensional point charge system with fullerene C60 lattice structure is calculated. Two kinds of electric

    field intensity distribution are given respectively: the x-axis ( i.e.,the central axis) is selected from the Pentagon

    center at the bottom to the Pentagon center at the top and the x-axis is selected from the hexagon center at the bottom

    to the hexagon center at the top. It is found that the electric field intensity at the center ( the original point) is

    zero. The electric field intensity on the central axis varies with the axial direction,but the distances between the

    maximum value of the electric field intensity in the axial direction and the center ( the original point) are the same.

    Preparation mode and practice of CUPT based on project-based learning   ——— taking Nanjing Normal University team as an example
    ZHOU Yang-ping, ZHONG Ming, LU Jian-long
    College Physics. 2021, 40(01):  75-79.  doi:10.16854 /j.cnki.1000-0712.200030
    Abstract ( 1223 )   PDF (1271KB) ( 438 )  
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    At the critical time point of ten years of Chinese Undergraduate Physics Tournament ( CUPT) ,the

    preparation mode formed from the experience is obtained in preparing for the competition by Nanjing Normal University

    CUPT team in the past ten years and the practice and exploration of cultivating undergraduate innovative talents

    based on CUPT and project-based learning ( PBL) are reported in this paper. The characteristics of the preparation

    mode are explained in detail in order to make CUPT continually play a positive role on the cultivation of undergraduate

    innovative talents based on the existing mode and achievements.

    The scientific thinking in the embryonic period of optics with the comparison of Chinese and Western civilization
    GAO Qi-ni, GUO Zheng-xin, DENG Hao-yi, OUYANG Min
    College Physics. 2021, 40(01):  80-84.  doi:10.16854 /j.cnki.1000-0712.200210
    Abstract ( 1396 )   PDF (1367KB) ( 810 )  
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    On the purpose of the Science Education,the teaching design of the general course module“Let

    there be the light”will be realized basing on the development history of the budding period of Optics in China and

    Western countries. It will guide students to understand the evolution process how different social groups in early human

    history understand the basic optical problems from subjective knowledge to objective understanding. We explore

    the development of the theoretical system of optical knowledge in this period,consider the impact of Chinese and

    Western civilization on the formation of scientific thinking and the evolution of research methods,understand the relationship

    between optical development and human civilization from a multidisciplinary perspective.