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Table of Content

    20 January 2018 Volume 37 Issue 1
      
    On the centenary of birth of R. Feynman,a great master of physics
    ZHAO Kai-hua
    College Physics. 2018, 37(1):  1-3.  doi:10.16854 /j.cnki.1000-0712.170508
    Abstract ( 1444 )   PDF (190KB) ( 1237 )  
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    The main scientific achievements and physics education paradigm of R.Feynman are reviewed.Understanding the natural laws deeply,R.Feynman spared the profound basic physics concepts to students or to the general public faithfully with his vivid language and humorous fables.
    Introduction to dimensional analysis
    LIANG Can-bin,CAO zhou-jian,CHEN zhi-tao
    College Physics. 2018, 37(1):  4-10.  doi:10.16854 /j.cnki.1000-0712.170262-1
    Abstract ( 1522 )   PDF (721KB) ( 2073 )  
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    A novel and systematic dimensional analysis is presented. A few new concepts such as “quantity class”and “class of unit systems”are coined, and a clear cut definition of “dimension”is provided. A self-contented proof of the theorem is presented based on these new concepts, and two examples illustrating the great power of the theorem are also given.
    Thinking about the limitation of wave function in quantum mechanics
    Sayipjamal Dulat,WANG Jian-hua,LV Teng-bo
    College Physics. 2018, 37(1):  11-13.  doi:10.16854 /j.cnki.1000-0712.170319
    Abstract ( 2926 )   PDF (183KB) ( 1030 )  
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    In quantum mechanics,the wave function must obey the three standard conditions,such as single value,continuous and finite,which give naturally energy quantization after the wave function under such conditions.The determination of convergence and divergence of infinite series is very important in quantum mechanics. The current textbooks use basically the same grade diverging to show that the series diverges.In comparison with divergent series,we adopt a more easy method to make students understand,find a better rather than the first series of small divergent series,and then prove little diverges,to illustrate that the series of great divergence.This interpretation not only enables students to accept quickly,more important is logically more complete.
    A study on topological properties of Aharonov-Bohm phase
    LUO Yun-wen
    College Physics. 2018, 37(1):  14-16.  doi:10.16854 /j.cnki.1000-0712.170074
    Abstract ( 1091 )   PDF (303KB) ( 741 )  
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    To construct an equivalent description of the two-level system with AB phase,we study the topological properties of the AB phase,and get the relationship between energy and magnetic field.It has found that the Aharonov- Bohm and Berry phases are essentially the topological and geometric phase of a kind.
    Solving the Wigner function of single-particle resonant state based on real stabilization method
    ZHANG Han1,LIU Zhi-wei1,REN Zheng-xue2,SUN Bao-yuan1
    College Physics. 2018, 37(1):  17-20.  doi:10.16854 /j.cnki.1000-0712.170117
    Abstract ( 1214 )   PDF (1640KB) ( 372 )  
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    Using the real stabilization method in coordinate space, the eigen-function of the single particle scattering state and resonant state in a one-dimensional potential are solved.In addition, the corresponding Wigner functions are given from the single -particle eigen -wave function,and the characteristic distribution of these Wigner functions in phase space is analyzed,which is proved to be a useful tool to distinguish the single-particle resonant state from the general scattering state and thus can be used as a criterion for studying the quantum properties in the relevant quantum measurement experiments.
    The definition of physics and the process of physical cognition
    MU Liang-zhu
    College Physics. 2018, 37(1):  21-24.  doi:10.16854 /j.cnki.1000-0712.170294
    Abstract ( 1665 )   PDF (311KB) ( 1232 )  
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    An explicit definition of physics is given.And a possible process of physical cognition is also concluded.
    An intuitive explanation for reactance of both capacitor and inductor in sinusoidal steady state
    WANG Jian,CAI Min,DONG Xing-fa
    College Physics. 2018, 37(1):  25-29.  doi:10.16854 /j.cnki.1000-0712.170338
    Abstract ( 1745 )   PDF (2342KB) ( 728 )  
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    Starting from the principle which inductors follow for energy storage,taking a one-order RL circuit driven by positive-negative pulse source as object and using math deduction,we get the relation between frequency and inductor's reactance in the steady state. The relation is also verified by using simulating experiment. Based on the same physical senses,i.e.,energy storage and charging-discharging,the explanation for the performance and properties of inductor in transient of dynamic circuit and in sinusoidal steady state circuit is given. The results are helpful to understand and master the concept of reaction of energy storage elements in the sinusoidal steady state.
    Axial symmetry magnetic vector potential and magnetic induction lines
    JIANG Jun-qin
    College Physics. 2018, 37(1):  30-36.  doi:10.16854 /j.cnki.1000-0712.170102
    Abstract ( 1580 )   PDF (2744KB) ( 753 )  
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    The distributions of the axial symmetry magnetic vector potential and the magnetic induction lines are studied by using Mathematica 10.3. The calculation formula of the magnetic vector potential A of the current carrying circular coil is expressed as the elliptic integral,the magnetic induction intensity B="×A and the magnetic induction line equation are deduced,the distribution maps of the magnetic vector potential and the magnetic induction lines are drawn, some defects of the distribution maps of the magnetic induction lines in the current literature are corrected. Then,the present method is applied to the current carrying tightly wound finite-length cylindrical solenoid and ellipsoidal coil.
    Solving Laplace equation by reduction dimension method based on conformal mapping andvisualization of electric field distribution
    JIANG Bao-jun1,WANG Fu-qian1,2
    College Physics. 2018, 37(1):  37-41.  doi:10.16854 /j.cnki.1000-0712.160065
    Abstract ( 1500 )   PDF (1551KB) ( 618 )  
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    With the help of the conformal mapping,we transform the domain of solution into the upper half plane or band domain,thus the dimensions of electric potential is reduced to 1 from 2,then the first boundary value problem of Laplace equation is solved easily. Meanwhile,the distributions of electric potential and electric field intensity are obtained,and the maps of both electric field land equipotential lines are plotted by using mathematical software MATLAB.
    Research on the coupling mechanism between a magnetic field and a sonoluminescing bubble by an approximate estimation method
    MO Run-yang,WANG Cheng-hui,HU Jing
    College Physics. 2018, 37(1):  42-45.  doi:10.16854 /j.cnki.1000-0712.170133
    Abstract ( 1148 )   PDF (238KB) ( 326 )  
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    In this paper, the potential various coupling mechanisms between the magnetic field and the sonoluminescing bubble were studied by a theoretical estimation method.The phenomenon of bubble sonoluminescence is an important way to reveal the mechanism of ultrasound cavitation.The magnetic field effects on the sonoluminescing bubble were studied from three areas, including outside the bubble, the bubble surface and inside the bubble.We also pointed the degree of importance of all possible various coupling ways bettwen the magnetic field and the sonoluminescing bubble and infered a interaction mechanisms from the effects.
    An analytic solution and asymptotic behavior for traction time of point charge to grounded conducting sphere
    LI Li1,ZHANG Yin2
    College Physics. 2018, 37(1):  46-47.  doi:10.16854 /j.cnki.1000-0712.1706165
    Abstract ( 1025 )   PDF (221KB) ( 342 )  
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    Under the conditions of irrespective gravity,air resistance and relativistic effect,this paper solves the relevant differential equation of motion directly,and obtains the analytic solution of traction time,which is expressed by the linear combination of Legendre complete elliptic integral of first and second kind. The asymptotic behavior is considered when sphere is changed into infinite plain,and then the same result with known literature is obtained.
    Energy of the damped harmonic oscillator in two-dimensional in Noncommutative Space
    WANG Ya-hui
    College Physics. 2018, 37(1):  48-50.  doi:10.16854 /J.cnki.1000-0712.170209
    Abstract ( 1183 )   PDF (212KB) ( 478 )  
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    The noncommutative space effect is a physical one in string scale. In this paper,the non-commutative ( NC) is introduced,which contains non-commutative of coordinate-coordinate,and the Moyal-Weyl product in noncommutative space can be replaced by a Bopp's shift. Then,the energy splitting of the damped harmonic oscillator in two-dimensional in non-commutative spaces are discussed.
    Airy wave packet and the auto acceleration effect(2)
    KONG Hong-Yan
    College Physics. 2018, 37(1):  52-54.  doi:10.16854 /j.cnki.1000-0712.170028-1
    Abstract ( 1168 )   PDF (309KB) ( 735 )  
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    Discussion on the effect of external space-time by the rotation of spherically symmetric weak gravitational source
    YANG Zhi-wan,HU Yan-fei
    College Physics. 2018, 37(1):  55-58.  doi:10.16854 /j.cnki.1000-0712.170127
    Abstract ( 1104 )   PDF (242KB) ( 305 )  
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    In this paper,the effect of the rotation of the unbalanced spherically symmetric weak gravitational source on the external space-time is analyzed by the Kerr metric. Such as how the spatiotemporal bending effect of the gravitational mass is affected by the rotation; how the length of the geodesic is affected by the rotation; how the symmetry of time and space is affected by the rotation.
    Energy effective bandwidth of non-sinusoidal wave and its energy truncation error
    CHEN Guo-jie,CHEN Kui,CHENG Jian-qun,XIE Jia-ning,CHEN Wei-cheng
    College Physics. 2018, 37(1):  59-63.  doi:10.16854 /j.cnki.1000-0712.170094
    Abstract ( 1309 )   PDF (572KB) ( 1117 )  
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    A method of evaluating the truncation error of the effective bandwidth is proposed. Taking a trapezoidal wave as a signal mode and using MATLAB calculations,the energy truncation error and physical nature of the effective bandwidth formula 0.35 /tr for a non-sinusoidal wave are analyzed,and the disadvantages of the bandwidth formula 1 /τ for an ideal rectangular wave are explained. The analysis results show that the truncation error of the effective bandwidth formula 0.35 /tr is less than 3%,and the truncation error of the formula 1 /τ is less than 10%. Therefore,the effective bandwidth formula for the ideal rectangular wave is modified to be 3 /τ. The bandwidths of a signal channel and an oscilloscope should be chosen greater than the effective bandwidths of the measured signals.
    Capacitance characteristics of PN junction devices under AC small signal
    WANG Li-ying,FENG Lie-feng
    College Physics. 2018, 37(1):  64-67.  doi:10.16854 /j.cnki.1000-0712.170075
    Abstract ( 1822 )   PDF (1078KB) ( 727 )  
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    GaN-based light-emitting diode ( LED) is a typical PN junction device. In this paper,GaN-LED is taken as an example to illustrate the capacitance characteristics of PN junction device under AC small signal. We have precisely pointed out the physical mechanism contributing to the total capacitance in different forward bias voltage intervals. Under a small forward bias voltage,the total capacitance of the PN junction is mainly contributed by the depletion layer capacitance. With the increase of the voltage,the total capacitance of the PN junction is mainly contributed by the diffusion capacitance. It increases with the voltage near an e-index. These characteristics are consistent with the classic Shockley theory that PN junction capacitance consists of depletion layer capacitance and diffusion capacitance. At large voltages,the PN junction capacitance becomes negative,which is defined as negative capacitance ( NC) . After accurately analyzing the NC characteristics,the empirical formula of the NC depending on voltage and frequency is summarized. The experimental results of NC cannot be explained by the classical Shockley's theory,but it provides a strong experimental foundation for Professor Hess's“Advanced Theory of Semiconductor Devices”,which will promote the development of semiconductor device physics.
    Gravitational waves and the 2017 Nobel prize for physics
    HUANG Yu-ao-tian1,ZHANG Xuan-zhong2
    College Physics. 2018, 37(1):  68-70.  doi:10.16854 /j.cnki.1000-0712.170556
    Abstract ( 1509 )   PDF (200KB) ( 846 )  
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    Gravitational wave exploration won the 2017 Nobel prize in physics,which means that this probe is a major verification of Einstein's general relativity,and is also the key to open the new era of gravitational wave astronomy. Therefore,it is important for the teachers,students and general readers to have a knowledge of the theory of gravitational waves. In this paper,the theory about gravitational waves is given with general relativity. We introduce how to calculate the amplitude of gravitational waves for binary black holes which rotating with each other.We also introduce the relationship of chirp mass and the frequency of gravitational waves.
    Research on teaching strategies of using interactive teaching model in the introductory physics class
    LUO Ying1,LIU Zhao-long2,LI Lie-ming3
    College Physics. 2018, 37(1):  71-76.  doi:10.16854 /j.cnki.1000-0712.170136
    Abstract ( 1372 )   PDF (552KB) ( 439 )  
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    The introductory physics course is an important and compulsory course of science and engineering universities; whose teaching quality has a crucial influence on that of following courses. At present,however,the traditional way of“indoctrination”is still the main teaching form at these universities. The singularity of its teaching method makes students have less opportunity to experience the fun of learning by themselves,which results in an inefficient class. Therefore,this situation is expected to be changed through a variety of teaching models and strategies. In this paper,the interactive teaching model is introduced and its characteristic is analyzed. And then through three comparative teaching experiments,it assesses and confirms the feasibility as well as the effectiveness of this model in the introductory physics course of Chinese science and engineering universities. Finally,it concludes with putting forward some interactive teaching strategies in the introductory physics course of science and engineering—improving the teaching quality with the help of network techniques,class responder and targeted instructional design according to students' needs and interests—to provide more diverse and attractive options for future courses.
    Research on mode of He-Ne laser based on Michelson interferometer
    MA Xiao-hang1,XIONG Chang2,TANG Fang2,WANG Hao-qiang1,NAN Yang3,LI Chao-rong2
    College Physics. 2018, 37(1):  77-80.  doi:10.16854 /j.cnki.1000-0712.170194
    Abstract ( 1264 )   PDF (639KB) ( 948 )  
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    This paper utilizes the Michelson interference to research the characteristics of the He -Ne laser. Combining the Fabry-Perot scanning interferometer and a Michelson interference experiment research,we analysis the polarization state of He-Ne laser's modes and the characteristics of frequency drift of He-Ne laser. We explain the spontaneous changes which observed in brightness and image of interference ring by theoretical derivation. Therefore,we have better comprehension on the characteristics of the multiple longitudinal-mode of the He-Ne laser.