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    20 June 2020 Volume 39 Issue 06
      
    Report on physics education in Peking University
    GUO Jiu-ling, ZHU Shou-hua
    College Physics. 2020, 39(06):  1-13.  doi:10.16854 /j.cnki.1000-0712.190403
    Abstract ( 1482 )   PDF (328KB) ( 642 )  
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    School of Physics of Peking University has the excellent tradition of physics education. In the last twenty or thirty years it experienced a great reform and reconstruction of the education system. Based on the opinions of the front-line teachers and together with the author’s own thinking on education，this paper is synthesized， sorted and refined. This paper attempts to make a summary of the existing excellent teaching tradition，advances educational ideas，flexible and efficient teaching management system，mature and reliable teaching methods and modes，etc. The authors wish that this comprehensive report could benefit the training of physics talents and the development of physics science.
    Electrostatic self-energy of a uniformly charged ellipsoid ———Sequel to“A supplement to the article‘Electric field in the cavity of a charged thick ellipsoidal shell’”
    YU Feng-jun, TANG Zhen-jie, TIAN Jun-long, JU Lin
    College Physics. 2020, 39(06):  14-17.  doi:10.16854 /j.cnki.1000-0712.190432
    Abstract ( 1633 )   PDF (653KB) ( 1217 )  
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    The electrostatic self-energy of a uniformly charged ellipsoid is calculated. The ellipsoid is composed

    of non-conductor. The method is to divide the thick ellipsoid into infinite thin coaxial ellipsoidal shells with the

    same eccentricity ratios. The electrostatic self-energy formula for a uniformly charged ellipsoid of general shape is

    obtained by considering the respective self-energy of every thin shell and interaction energy for each other.

    Research on the virtual image position of inclined chopsticks in a bowl filled with water
    SHAO Yun
    College Physics. 2020, 39(06):  18-24.  doi:10.16854 /j.cnki.1000-0712.190348
    Abstract ( 1973 )   PDF (1933KB) ( 621 )  
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    Based on the existing optical knowledge，this paper deduces the coordinate expression of virtual image

    points of chopsticks inserted obliquely at 30 degrees into the bowl full of water when one looks down from the

    front and side. The three-dimensional curves of virtual image of chopsticks under various typical observation situations

    are drew. It is pointed out that when one observes from the side，the virtual image of chopsticks should be a

    curve even in the sense of sight. The virtual images of chopsticks observed at 30 cm visual distance and ∞ far visual

    distance are compared when one looks down from the front and vertical side，the difference between them is greatest

    when the angle of view is near 60 degrees. The virtual images of chopsticks seen by the left and right eyes at 30 cm

    visual distance overlooking from the front and vertical sides are calculated and made，the difference between the two

    images increases with the increase of visual angle. Finally，the origin of the coordinate expression of virtual image

    points of chopsticks is explained，and the advantages of the analytical results are pointed out.

    Teaching investigation on Schrödinger's equation
    HUANG Yong-yi
    College Physics. 2020, 39(06):  25-26. 
    Abstract ( 950 )   PDF (117KB) ( 607 )  
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    The paper introduces the Schrödinger’s equation from wave equation and de Broglie relation. The introduction method is more natural than the present methods in the popular textbooks.

    Influence of damping sheets on the forced vibration of tuning fork under different conditions
    LI Chao-gang, YI Shi-fan, PENG Xue-cheng, HUANG Wan-xia
    College Physics. 2020, 39(06):  27-32.  doi:10.16854 /j.cnki.1000-0712.190435
    Abstract ( 1473 )   PDF (1485KB) ( 813 )  
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    The effects of the area，shape，fixed angle and relative position of damping plate on the forced vibration

    system of the tuning fork are studied experimentally. The experimental results have shown that the square of

    the period is proportional to the area of the damping plate under the same shape. Damping plate with the same area

    and different shapes have different resonance frequencies and sensitivities. The sensitivity of the rectangle is larger，

    and the sensitivity of the triangle is smaller. The resonance frequency of forced vibration of the tuning fork is related

    to the fixed position and the angle of the damping plate with the same shape and area. The result obtained in this research

    is certain guiding to the design of tuning fork sensor.

    Transmission characteristics of resonant magnetic coupled wireless 　　power transmission system and design of experiment instrument
    CHEN Guo-jie, ZHOU You-ping, YAN Dong, XIE Jia-ning, LI Bin
    College Physics. 2020, 39(06):  33-38.  doi:10.16854 /j.cnki.1000-0712.190324
    Abstract ( 1690 )   PDF (1068KB) ( 1762 )  
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    The transmission characteristics of a magnetic coupled wireless power transfer system are analyzed

    based on the magnetic coupling theory，and an experiment instrument of the resonant magnetic coupled wireless

    power transfer system is developed. The transmission characteristics of the system are visually observed under the

    LED load. The high frequency equivalent resistance of the transmitting coil is measured. The condition of maximum

    output power and the law of frequency splitting are obtained by exploring the relations between the output power and

    the signal frequency，transmission distance，or load of the system. The results indicate that the trend-skin effect of

    the high frequency coil is obvious; and the higher the frequency is，the greater the equivalent resistance. The resonant

    characteristics of the magnetic coupled wireless power transfer system are not only related to the transmission

    signal frequency and the inherent frequency of the receiver and transmit circuit，but also linked to their coupling coefficient;

    the output power as well as the transmission efficiency is maximized at the optimal full resonance. Our design

    experiment instrument can be generalized to measure the stable characteristics of RLC series circuits，and operate

    stably. The experimental results are consistent with the theory.

    Research on symmetry breakage in Hall effect experiment
    GAO Qian, ZHU Ya-min, YU Chun-xu, ZHU Jiang
    College Physics. 2020, 39(06):  39-43.  doi:10.16854 /j.cnki.1000-0712.190344
    Abstract ( 1392 )   PDF (603KB) ( 705 )  
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    So far，it has been still necessary for obtaining the types of electrical conductivity in semiconductor

    materials and many parameters obtained to use Hall effect experiment. So，Hall effect experiment is a very

    important classical experiment. However，at the same time as Hall effect happens，there are a lot of side effects.

    The measured value of Hall effect voltage always deviates from its real value. It results in a certain deviation of

    measured parameters. In practice，the symmetrical measurement is often used to eliminate the influence of side

    effects. However，there is symmetry breaking in the data columns which are measured by the symmetric measurement.

    Considered the carrier's motion，the origin of symmetry breaking is gradually analyzed which is the joint action

    of an electric field and a magnetic field. And magnetic field is stronger than electric field in symmetry breaking.

    So that semiconductor material properties is studied.

    Study of the diffraction characteristics of terahertz wave
    ZHAN Hong-lei, QIN Fan-kai, ZHAO Kun, CHEN Si-tong
    College Physics. 2020, 39(06):  44-46.  doi:10.16854 /j.cnki.1000-0712.190328
    Abstract ( 1319 )   PDF (853KB) ( 654 )  
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    The diffraction characteristics of terahertz waves are analyzed and explored by using different width

    of diffraction screens. According to the terahertz wave diffraction characteristics，the width variation of the

    diffraction screen is divided into three stages. The optical path variation and intensity distribution of the terahertz

    wave are reflected by the time delay and peak amplitude parameters of the terahertz time-domain spectrum. The experiment

    can be used as an extension of the knowledge of diffraction in light in class and as an example of the combination

    of diffraction theory and practice in physics teaching.

    Improving the blending teaching result for the large-class college physics with the help of information technology
    YU Shu-yun, GE Mei-hua, WANG Hong-chao, LIU Jian-qiang
    College Physics. 2020, 39(06):  47-51.  doi:10.16854 /j.cnki.1000-0712.190445
    Abstract ( 1148 )   PDF (604KB) ( 460 )  
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    The design and practice of the blending teaching method for the large-class college physics based on

    SPOC in Shandong University are described. The students - centered teaching concept is the center through the

    whole process. The problem-based teaching method has been used to stimulate the study initiative of the students

    for the online study. With the help of the Rain Classroom，the mutual-motivation teaching is used to encourage the

    class participation and to improve the students’integrative ability for the offline study. Our experience over the

    years has proved that the blending teaching mode combined with traditional face-to-face teaching should effectively

    improve the teaching result for the large-class college physics.

    Rain classroom: Practice and reflection on the teaching of 　　“multi-dimensional and different levels”
    ZHU Chun, CHEN Guo-qing, NIE Yan-guang, WU Ya-min
    College Physics. 2020, 39(06):  52-58.  doi:10.16854 /j.cnki.1000-0712.190364
    Abstract ( 1940 )   PDF (454KB) ( 662 )  
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    In the context of mobile internet，the combining between“rain classroom”and“divisional teaching

    mode”is used in the practice of university physics experiment teaching. Hierarchical teaching of the same teaching nature

    class is realized in the three dimensions before class，classroom and after class. The introduction of the rain classroom

    fundamentally solves the problem of low classroom efficiency in the teaching mode of different layer-same classdifferent

    method，especially for students who do not have physics in the college entrance examination. Multi-dimensional

    hierarchical teaching based on rain classroom not only stimulates students' enthusiasm for learning，meets the learning

    needs of students，but also realizes personalized and effective teaching and enhances teachers’sense of accomplishment.

    Effect of China Undergraduate Physics Tournament on improving the ability of undergraduates at different aspects
    JIN Kang, WANG Xiao-hui, HE Qing-li, ZHENG Xin-liang
    College Physics. 2020, 39(06):  59-64.  doi:10.16854 /j.cnki.1000-0712.190535
    Abstract ( 1677 )   PDF (1118KB) ( 958 )  
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    China Undergraduate Physics Tournament ( CUPT) has been held for 10 times since 2010. Nowadays，

    this tournament has become an important capacity training， scientific research training and academic exchange

    platform for undergraduates majoring in physics. In this article， it is demonstrated that the CUPT could effectively

    promote the students who attended CUPT to master various of application software，expands their learning and exploration

    and carries out scientific research by analyzing the information of the using of tool software， the physical

    branch disciplines involved，and the results related to tournament. In addition， the development of CUPT at Northwest

    University and its role in enhancing students' autonomous learning and research capabilities are also described.

    Can Rutherford's cannon balls bounce back?
    LIU Zhi-hua, LUO Cheng-lin
    College Physics. 2020, 39(06):  65-67.  doi:10.16854 /j.cnki.1000-0712.190385
    Abstract ( 1286 )   PDF (313KB) ( 874 )  
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    The core concept of atomic physics is the atomic model. In all the atomic physics textbooks，

    Thomson's model of atomic scattering of the alpha particle is the most basic content，but in the teaching process，

    generally only starting from the classical mechanics of alpha particle scattering theory deduction，few of error transfer

    and mathematical statistics knowledge were discussed. In this paper，starting from the related theory of classical mechanics

    and mathematical statistics，we calculate the probability of alpha particle large angle scattering in the experiment

    of Rutherford scattering experiment. In order to show that in the teaching process should strengthen，their ability

    of multidisciplinary knowledge fusion is the key step to improve students'scientific research ability.

    Research and experiment of indoor visible light positioning technology based on fast Fourier transform
    YOU Ying-xuan, LU Zhe-rui, WANG Wen-ling
    College Physics. 2020, 39(06):  68-73.  doi:10.16854 /j.cnki.1000-0712.190465
    Abstract ( 1232 )   PDF (1190KB) ( 858 )  
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    In order to solve the problem of the complexity of indoor positioning system and unsatisfactory response

    time， this paper uses Fourier transform to process square-wave modulated optical signals to reduce the response

    time，and optimizes the reflection effect of optical signals in the transmission process， then establishes a positioning

    system model with high accuracy and fast response time.Based on the function describing the relation of light

    intensity and distance， the correction of the incline plane has been founded which helps to solve the coordinates of　

    the receiver.By applying the theory to the positioning device， the visible light positioning system with fast response

    and high precision is finally realized.

    Thermoelectric conversion device based on Seebeck effect
    Lü Nan, LIU Zuo-lian, JIE Hai, ZHANG Cheng-yun
    College Physics. 2020, 39(06):  74-77.  doi:10.16854 /j.cnki.1000-0712.190334
    Abstract ( 1585 )   PDF (701KB) ( 847 )  
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    Thermoelectric power generation is a new kind of environment-friendly energy technology with reliable

    performance which can transfer waste heat energy into electricity. The device of thermoelectric conversion based

    on Seebeck effect is designed in this paper. Based on single chip processor and OP07 chip， the active I /V conversion

    circuit is designed and the output voltage was displayed on the LCD1602. The output power from different temperature

    differences is calculated and compared. The experimental result shows that the voltage generated from the

    device increases linearly with the temperature difference，and the thermoelectric conversion efficiency of the device

    is about 0.11%. The device can supply power to equipment with small power consumption.

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