Top Read Articles

Published in last 1 year |

In last 2 years |

In last 3 years |

All

Please wait a minute...


For Selected: Download Citations EndNote Ris BibTeX Toggle Thumbnails

Select

Several mean-value relations of a moving mass point  on elliptic trajectory under inverse squared centric force ZHOU Guo-quan, TANG Yu-xuan, QI Ning College Physics    2023, 42 (8): 6-.   DOI: 10.16854/j.cnki.10000712.220359 Abstract （928）      PDF（pc） （498KB）（987）       Knowledge map    Save  Based on Kepler's three laws, and the conservation laws of mechanic energy and angular moment about a mass point moving on an elliptic trajectory under an inverse-squared centric force, the mean values within a period of some typical physical quantity (polar radiurs，speed, angular speed, angular momentum, rotation inertia, kinetical energy，potential energy，and so on) ，are calculated and several interesting and useful mean-value relations are found and proved. A unique mean-value point on the path of the mass point is emphasized. The Virial theorem is direct proved by means of these calculated mean values. The physical meanings, and teaching reference significance of these findings are also emphasized. Related Articles | Metrics | Comments（0）

Select

Notes on the Green,s function method YANG Shi-jie College Physics    2023, 42 (8): 1-.   DOI: 10.16854/j.cnki.1000-0712.220596 Abstract （480）      PDF（pc） （564KB）（574）       Knowledge map    Save The paper systemically describes the fundamental principle of the Green,s function method. It demonstrates that the reversal relation holds only for the case of self-adjoint operator. The homogeneous boundary condition of the Green,s function also comes from the self-adjointness of the differential operator while the Green integral formula does not directly apply to the non-self-adjoint operator. The paper also addresses perturbation expansion method induced by the Green,s function, shows its relation to the popular Feynman diagram technique in physical science so as to help the student understanding the internal logics when learning advanced physics. Related Articles | Metrics | Comments（0）

Select

Analysis of conservation of momentum and angular momentum in collision problems QIU Hong-mei, QIN Ji-hong, XU Mei, LIU Li-hua College Physics    2023, 42 (10): 2-.   DOI: 10.16854/j.cnki.1000-0712.230039 Abstract （462）      PDF（pc） （772KB）（479）       Knowledge map    Save In this paper, the most typical collision problem between an object and a slender bar in rigid body mechanics is taken as an example, and the application conditions of the law of conservation of momentum and conservation of angular momentum are discussed from the perspective of force analysis, in order to deepen the understanding of the two conservation laws, hoping to play a certain reference role for teachers' teaching or students' self-study Related Articles | Metrics | Comments（0）

Select

Critical-slowing-down of nonlinear systems at bifurcation points ZHANG Jie, DU Yao, LI Qing, YU Yi-zhen, LI Hai-hong, WANG Xin-gang College Physics    2023, 42 (05): 9-.   DOI: 10.16854/j.cnki.1000-0712.220240 Abstract （459）      PDF（pc） （560KB）（314）       Knowledge map    Save As a key concept in nonlinear science, Lyapunov exponent has been extensively studied in literature. In general, to analyze the stability of a dynamical state, it is the sign of the Lyapunov exponent that is interested. Yet, this approach fails when the state is located exactly at the bifurcation point, where the Lyapunov exponent is equal to zero, suggesting that the perturbations will be keeping unchanged during the system evolution at this point. This prediction, however, is conflicting with the true results, as attractors also exist at the bifurcation points. Here we are able to argue mathematically and demonstrate numerically that at the bifurcation points the perturbation is damped by a power-law scaling to the equilibrium, with the scaling exponent determined by the nonlinear term of the variational equation of the perturbations. That is, the dynamics of the system shows the typical feature of critical slowing down observed at the critical point of many physical systems. The phenomenon of critical-slowing-down is demonstrated in different nonlinear models, and the theoretical predictions are in good agreement with the numerical results in all cases studied. Related Articles | Metrics | Comments（0）

Select

Research on Boycott effect of the particles based on PNK theory SHAO En-hao, TUERSUN Paerhatijiang College Physics    2023, 42 (05): 61-.   DOI: 10.16854/j.cnki.1000-0712.220363 Abstract （457）      PDF（pc） （446KB）（221）       Knowledge map    Save The Boycott effect was discovered by Boycott that oxalated or defibrinated blood corpuscles sediment much faster in an inclined tube than in a vertical one. This paper derivatives research whether the sedimentation of insoluble particles in oblique vessel filled with distilled water also has boycott effect and investigate the effect of relevant parameters. Refer to PNK theory to study the influence of the three parameters on the settlement rate that affect the system, namely suspension interface velocity in a vertical container, the width of the container, and the angle of inclination. At the same time, through experiments, the effect of different parameters on sedimentation rate is explored, and compared with the theoretical analysis. The results show that insoluble particles also has boycott effect; as the angle of inclination increases, the sedimentation rate of the particles in it increases first and then slows down; the width of the container and the suspension interface velocity in a vertical container is always positively correlated with the sedimentation rate. Related Articles | Metrics | Comments（0）

Select

Solving Helmholtz equations in cylindrical coordinate system and its typical application in electromagnetism MA Zi-yin, CHEN Wen-qiong, MEI Zhong-lei College Physics    2023, 42 (10): 15-.   DOI: 10.16854/j.cnki.1000-0712.230065 Abstract （451）      PDF（pc） （931KB）（352）       Knowledge map    Save Helmholtz equation is a kind of elliptic partial differential equation, which is used to characterize the propagation law of electromagnetic wave. When solving Helmholtz equation in cylindrical coordinate system, most textbooks use the method of separating variables to introduce, but most textbooks do not have a detailed classification and discussion of the results of separating variables, nor do they explain its practical application, which makes it difficult for beginners to understand and master physical meanings. In this paper, the Helmholtz equation is solved by the method of separating variables, the form of solution is discussed systematically, and the typical applications of various results are analyzed by means of electromagnetic simulation and numerical calculation. It has a certain reference significance for the teaching and research of electromagnetic field theory. Related Articles | Metrics | Comments（0）

Select

The effect of quantity momentum in modern quantum physics WANG Hai-jun College Physics    2023, 42 (6): 1-.   DOI: 10.16854/j.cnki.1000-0712.220463 Abstract （441）      PDF（pc） （823KB）（698）       Knowledge map    Save  Nowadays the public's familiarity with classical momentum is almost as good as energy. The law of conservation of momentum is deeply rooted in the hearts of the people. The center collision effect of equal-mass balls is even used in entertainment programs and dances. This article demonstrates the application of quantum momentum by estimating several typical physical examples in quantum theory, leading readers to reveal the nature of momentum step by step, and also enable readers to deeply understand the physics of wave functions in quantum mechanics.  Related Articles | Metrics | Comments（0）

Select

A brief discussion on variational principle and some applications ZHENG Shen-zhou, YU Hai-yan College Physics    2023, 42 (10): 1-.   DOI: 10.16854/j.cnki.1000-0712.230014 Abstract （419）      PDF（pc） （783KB）（445）       Knowledge map    Save  The variational principle is introduced, and its Euler-Lagrange equation for the minimum of variational problems in the setting of one dimension is described. Then, the corresponding specific expression of these Euler-Lagrange equations for taking a geodesic line, geodesic curve, Brachistochrone and isoperimetric problems are deduced as examples, respectively. The solutions of the corresponding original problems are obtained and the relevant generalizations are given. Related Articles | Metrics | Comments（0）

Select

Optimizing method and quantitatively evaluation on experimental conditions for Frank-Hertz experiment LI Chao-rui College Physics    2023, 42 (7): 28-.   DOI: 10.16854/j.cnki.1000-0712.220551 Abstract （399）      PDF（pc） （1158KB）（569）       Knowledge map    Save  Frank-Hertz experiment has substantial physics content，and the optimization of its experimental conditions has been extensively discussed in the past.It is a right choice to clearly understand experimental physics by introducing experimental optimizing method and its physical judgment.The preliminary experimental results are obtained by using default parameters provided by equipment manufacturer.On the basis of measurement principles，the collector potential is set to be close to but less than the experimental excitation potential.Then，the filament voltage (current) is appropriately adjusted according to the influence of filament temperature on hot electron emission density.Finally，the first grid potential is changed and its influence is observed.The experimental optimization level is quantitatively evaluated with an indicator defined as the mean and standard deviation of collector current values at the peak and the valley.The accurate experimental results can be obtained on the optimal experiment condition. Related Articles | Metrics | Comments（0）

Select

Hydrogen atom energy levels and wave functions based on  Gaussian expansion method PAN Ya-wen, GENG Li-sheng College Physics    2023, 42 (05): 18-.   DOI: 10.16854/j.cnki.1000-0712.220263 Abstract （395）      PDF（pc） （389KB）（309）       Knowledge map    Save  In this paper, the Gaussian expansion method is used to accurately solve the Schrodinger equation of the hydrogen atom and obtain its energy levels and wave functions. The influence of the selection of variational parameters in the Gaussian expansion method on the accuracy of the results is studied. The program is written in Python, and this method and accompanying code can be beneficial to teachers and students in teaching and learning computational physics and quantum physics. Related Articles | Metrics | Comments（0）

Select

Solution of Schrödinger equation in a 1D homogeneous field REN Xi-jun, LIU Xiang-rui College Physics    2023, 42 (7): 3-.   DOI: 10.16854/j.cnki.1000-0712.220552 Abstract （360）      PDF（pc） （661KB）（862）       Knowledge map    Save The solution of time dependent Schrödinger equation in a one-dimensional homogeneous field is carried out in detail. The idea is, based on the classical trajectory of a classical particle in the homogenous filed, the time dependent wave function can be constructed from this trajectory with a phase factor function which is determined by solving the Schrödinger equation. Guided by this idea,  the propagator function of homogeneous field is obtained for both position representation and momentum representation. Meanwhile, Dirac notation for state vectors is employed to obtain the above results for comparison. Related Articles | Metrics | Comments（0）

Select

Study on the isotropic property of semiconductor conductivity effective mass XU Jie College Physics    2023, 42 (7): 1-.   DOI: 10.16854/j.cnki.1000-0712.220570 Abstract （345）      PDF（pc） （753KB）（559）       Knowledge map    Save In this paper the expression of electron effective mass of semiconductors is deduced when the 3D kspace equienergy surfaces are not spherical by using multivariable calculus and tensor analysis. Then, it is discussed whether the conductivity effective mass tensors of Si and Ge are isotropic. The discussions can promote students′ understanding of energy band structures of semiconductors and its influence on conductivity. Related Articles | Metrics | Comments（0）

Select

A new teaching model of college physics integrated with IYPT PAN Gang, CHEN Wen-juan, FANG Lian College Physics    2023, 42 (05): 51-.   DOI: 10.16854/j.cnki.1000-0712.220456 Abstract （345）      PDF（pc） （467KB）（156）       Knowledge map    Save Traditional college physics teaching is mainly taught by teachers，and students' learning mainly depends on memory and understanding，which leads to unidirectional teaching process.Due to the lack of effective carrier for interaction and the lack of personal experience of physics knowledge，students gradually lose their interest in learning college physics. In this paper，IYPT is integrated into college physics classroom，and students are guided to comprehend and apply knowledge in the process of solving problems，so as to form a new mode of college physics teaching. Through four years of teaching practice，it has found that this teaching model has a certain role in promoting students, ability in the aspects of unified examination and competition. Related Articles | Metrics | Comments（0）

Select

Relativistic induced electromotive force and calculation  for it under transformation of reference frame College Physics    2023, 42 (05): 38-.   DOI: 10.16854/j.cnki.1000-0712.220206 Abstract （334）      PDF（pc） （237KB）（320）       Knowledge map    Save The relativity between motional and induced electromotive forces is investigated. The reasons are analyzed for the variation in value of total induced electromotive force for different reference frames. A general formula is proposed for calculating the total induced electromotive force under transformation of reference frame. The total induced electromotive forces of rectangular and circular coils moving outside an infinity long wire carries direct current are calculated. The total induced electromotive force measured by the moving observer is equal to the sum of the electromotive forces measured at different positions of the conductor with different times by the stationary observer. Related Articles | Metrics | Comments（0）

Select

Introduction of quantummachine learning and its application in a certain scenario ZHU Qin-sheng, YANG Shi-lu, LIU Heng-yu, TENG Bao-hua College Physics    2023, 42 (8): 27-.   DOI: 10.16854/j.cnki.1000-0712.220509 Abstract （334）      PDF（pc） （551KB）（514）       Knowledge map    Save In the past few decades, machine learning showed a profound impact on all kinds of industries. In recent years, researchers have combined quantum computing with machine learning, and proposed quantum machine learning to realize the acceleration of traditional algorithms. At present, the applications of quantum machine learning in physics, chemistry, finance, biomedicine and other fields have attracted great attention. This paper first introduces the basic concepts of quantum machine learning and the current advances. Secondly, taking hydrogen fluoride（HF） molecule as an example, we discuss the application of quantum machine learning in the calculation of ground state energy of physical systems and also demonstrate the role of quantum machine learning. Related Articles | Metrics | Comments（0）

Select

Research and practice of curriculum ideological and political education of mechanics in college physics SHI Guo-fang, YANG Chao, LI Jing-ling College Physics    2023, 42 (10): 38-.   DOI: 10.16854/j.cnki.1000-0712.220600 Abstract （333）      PDF（pc） （906KB）（472）       Knowledge map    Save Curriculum ideological and political education is a strategic measure of realizing the basic task of morality education in universities. In this article, the present situation of curriculum ideological and political education is analyzed, then taking mechanics as an example, many ideological and political elements in mechanics are explored and provided from four aspects. The technique and principle during curriculum ideological and political education are also pointed out, and the result shows that curriculum ideological and political education in college physics is beneficial to the character shaping and all-round development of students. It is widely praised by students. Related Articles | Metrics | Comments（0）

Select

Connective problems of the wave equation at interfaces YANG Shi-jie College Physics    2023, 42 (11): 1-.   DOI: 10.16854/j.cnki.1000-0712.230051 Abstract （326）      PDF（pc） （245KB）（389）       Knowledge map    Save The paper investigates eigen modes of the wave equation in discontinuous media and explores the underlying physical mechanism. We also study the reflection and transmission of wave at the interface and reveal a full transmission effect under specific physical conditions. This effect may find applications in wave-absorptive materials. Related Articles | Metrics | Comments（0）

Select

Complex relationships of angular momentum of rotating rigid-bodies ——Discussing the significance of choosing the right reference frame DONG Ke, ZHOU Yu-qing, College Physics    2023, 42 (11): 5-.   DOI: 10.16854/j.cnki.1000-0712.230023 Abstract （321）      PDF（pc） （958KB）（345）       Knowledge map    Save A seemingly simple rigid-gyro-motion problem involves an overlooked aspect in university physics teaching, namely, the calculation of angular momentum when rigid bodies rotate simultaneously around mutually perpendicular axes. Starting from the solution of question, this paper elaborates the complex relationship of angular momentum of rigid-body (gyro) rotation, and derives the correct angular momentum transformation relationship of simple and constrained gyroscope. At the same time, it shows that, this kind of problems can be greatly simplified when selecting the appropriate reference frame. Related Articles | Metrics | Comments（0）

Select

Extension and analysis of a problem on  double-conductor-sphere electrostatic induction LI Zhao-yu College Physics    2023, 42 (8): 11-.   DOI: 10.16854/j.cnki.1000-0712.220435 Abstract （308）      PDF（pc） （956KB）（437）       Knowledge map    Save A problem on the electrostatic induction of double conductor spheres and its solution are presented,and several problems are derived from it. Based on the basic idea of the mirror method, a mirror-charge construction method is designed for solving the electrostatic induction of any multiple charged conductor spheres, and the above problems are solved numerically to obtain the spatial potential and electric field in the symmetric and asymmetric cases, respectively. The charge density distribution curves on the sphere of the conductor are plotted and their physical significance is discussed. Related Articles | Metrics | Comments（0）

Select

Theoretical and experimental study of transverse vibration of string, beam and ring FANG Yi-zhong, CUI Xin-tu, SHEN Han, HUANG Zhen-cheng, FENG Rao-hui, LIAO De-ju, PANG Xiao-ning College Physics    2023, 42 (6): 32-.   DOI: 10.16854/j.cnki.1000-0712.220466 Abstract （305）      PDF（pc） （886KB）（523）       Knowledge map    Save From the strict derivation of transverse vibration of string, the explicit solution of wave velocity is obtained. Through measuring the wavelength and eigen frequency of resonance, the experiment value of wave velocity is also obtained, which is well agreed with the theoretical value. The transverse vibration equation of beam is also solved exactly. The simulation of the problem which one end is clamped and the other is free, is performed. The expressions of first several resonant eigen frequencies and the sites of standing-wave nodes are obtained so as to get the general solution. Further, the fundamental frequencies and resonant frequencies of the previous order overtone of steel slender strips under different lengths are measured. The co-ordinates of standing-wave nodes are observed and equivalent to the theoretical results, and the Young’s modulus of the strips are calculated, which are well corresponded with standard values. Furthermore, the case of small radial vibration of ring is popularized. The resonant frequencies and wavelengths are also measured, and the elastic modulus of circular cross section ring are obtained, where are also accorded with the existing values.  Related Articles | Metrics | Comments（0）