Table of Content

13 April 2021 Volume 40 Issue 4

  

Some thoughts on teaching solid state physics II: an example of the frontiers in magnetism

YUAN Zhe

College Physics. 2021, 40(4):  1-5.  doi:10. 16854 /j. cnki. 1000-0712. 200451

Abstract ( 1304 )   PDF (452KB) ( 842 )  

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Solid state physics is an important course for undergraduate students of physics，and its contents are

closely related to the research frontiers of condensed matter physics. Introducing appropriate latest progress in the

teaching can expand students’scientific level and encourage them to pursue further studies and researches. In this

paper，domain-wall resistance in ferromagnetic metals in the chapter of magnetism in solid states is taken as a typical

example and a guidance for students is provided to analyze the spin dependent transport in magnetic domain

walls. In this process， the students need to integrate the knowledge they have learned including the energy band theory，

perturbation theory and transport phenomena in quantum mechanics and solid state physics. By systematically illustrating

this typical example， the integration of the cutting-edge research of spintronics into teaching solid state

physics is demonstrated which would be a useful reference for creating a high -level， innovative and challenging

course of solid state physics.

A more general proof on“Nuclear reaction being completely inelastic collision when incident particle having threshold energy”

SU Guo-zhen

College Physics. 2021, 40(4):  6-7.  doi:10. 16854 /j. cnki. 1000-0712. 200221

Abstract ( 1404 )   PDF (218KB) ( 473 )  

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A more general proof on“Nuclear reaction being completely inelastic collision when incident particle having threshold energy”is presented.

The characteristic derivation method of Maxwell s rate distribution

FENG Shi-meng

College Physics. 2021, 40(4):  8-10.  doi:10. 16854 /j. cnki. 1000-0712. 200485

Abstract ( 2665 )   PDF (253KB) ( 1326 )  

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A basic point in college physics teaching is to cultivate students' spatial imagination. Maxwell's rate

distribution law is a central content of the gas molecule kinetic theory，which is difficult for students to learn and

professors to teach during the teaching process of gas dynamics theory. Its formula is abstract，complicated and difficult

for students to understand. Based on the concept of velocity space， it is presented the surface area of the velocity

sphere is equivalent to the number of microscopic states of a single gas molecule，and the Langerian function is used

to derive the velocity distribution function of gas molecules in the ideal gas equilibrium state. This method is relatively

simple and easy for students to understand is helpful to cultivate their spatial imagination.

The influence of atomic mass on the dispersion relation of one-dimensional three-atom chain

ZHAO Yuan, HU Jian-min, WANG Yue-yuan, NIU Li

College Physics. 2021, 40(4):  11-14.  doi:10. 16854 / j. cnki. 1000-0712. 200407

Abstract ( 1938 )   PDF (737KB) ( 487 )  

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In this paper，the numerical analysis method is used to study the influence of the atomic

mass in the primitive cell on the dispersion relationship of one-dimensional three- atom chain.

The basic law of the spectral width and the frequency band gap changing with the atomic mass are established. The results show

that when the mass of only one atom in the primitive cell changes，the width of the acoustic wave spectrum decreases with the increase

of any atomic mass. The spectral width of optical waves increases with the increase of the mass of small atoms，and decreases with the increase of the mass of large atoms. Both frequency band gaps are narrowed with increasing the mass of the small atom，and widened with increasing the mass of the large atom. As the mass of the intermediate atoms increases，the frequency forbidden band between low-frequency optical waves and acoustic waves gradually is narrowed，while the frequency forbidden band between high-and low-frequency optical waves is gradually widened. The rel-evant results provide a theoretical basis for the design of crystal band-pass filters.

Design of a horizontal Young's modulus instrument and assembling a platform scale

LI Cheng-long, CHANG Fang-jin, SHOU Hua-jie , SHEN Qi-kai

College Physics. 2021, 40(4):  15-18.  doi:10. 16854 /j. cnki. 1000-0712. 200015

Abstract ( 1304 )   PDF (699KB) ( 400 )  

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Based on the stress analysis of steel wires placed horizontally，the measuring formula

of the young's modulus is derived，and then it is measured experimentally. Using the value of

young's modulus as a known parame- ter and steel wire as a strain sensor of the pressure，a simple

platform scale is designed and its measuring formula is derived to measure the gravity of unknown

object. Such a design makes the traditional confirmatory experiment im- prove to a designing

experiment，reduces the experimental error and also enriches the experiment contents.

Analysis of liquid equilibrium state under the rotating mode

LEI Yi, SHI Li-hong, ZHANG Jun-cheng, PAN Jian-peng

College Physics. 2021, 40(4):  19-21.  doi:10. 16854 / j. cnki. 1000-0712. 200143

Abstract ( 1563 )   PDF (585KB) ( 252 )  

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This paper studies equilibrium liquid level formed by the rotation of liquid on the

wall，the equation is deduced when the slop of the wall is K ( K≠0) . When K→∞ ，the change of liquid

level is infinite with the in- crease of rotating speed，but the rise height of liquid level is

equal to the fall depth of liquid level，and the volume relationship is a constant. when K>0，the

container is a round table with large top and small bottom. The liquid level

change caused by rotating paraboloid is limited，and the limit value is槡3 +1，when the liquid

rotation angular veloci- ty exceeds the critical angular velocity，the rotating liquid surface

is divided into two parts: the paraboloid in the middle and the water film with growing edge.

A double-beam interference apparatus with a regular triangle structure

ZHOU Guo-quan

College Physics. 2021, 40(4):  22-26.  doi:10. 16854 / j. cnki. 1000-0712. 200135

Abstract ( 2718 )   PDF (557KB) ( 883 )  

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An optical interference apparatus with a regular triangle structure，which can

generate double - beam interference，is introduced according to the optical wave theory. The

formulae of optical path difference and phase difference have been derived; the

interference conditions and distribution laws of spots or fringes are also quantitatively

analyzed in detail. Its possible application and supplement function in teaching and researching

activ- ities are also discussed.

Terahertz spectral analysis of emulsion combined with effective medium theory

LI Chao, QIN Fan-kai, MENG Zhao-hui, CHEN Ru, YANG Qi,

College Physics. 2021, 40(4):  27-31.  doi:10. 16854 / j. cnki. 1000-0712. 200314

Abstract ( 1496 )   PDF (1477KB) ( 367 )  

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Crude oil emulsions have an important influence on the long-distance transportation of crude oil. The oil and water state of the emulsion and the interaction mechanism require new theories and new methods. The terahertz spectrum ( THz- TDS) response of

crude oil emulsion is studied based on the effective medium theory. The THz-TDS of emulsions with water content of 0 ～ 28 % are obtained by using the THz-TDS system. The optical parameters such as absorption coefficient and dielectric constant are calculated by

Fourier transform. The optical parameters increase with the increase of water content of emulsions. The actual dielectric constant is consistent with the dielectric constant calculated by Bruggeman's theory，and the maximum error rate is less than 3 % . The results show that when the

water content is small，the water is dispersed in the crude oil，the distance between the particles is large，and the interaction force between the particles is small. As the water content increases，the water phase and the oil phase are mixed and distributed，the distance between the

particles will become smaller，and the inter- action force of the particles will become larger.Therefore，the effective medium theory is significant to investigate the THz spectrum of oil-water emulsions.

A practical exploration of the teaching mode of PAD class in college physics

QIN Dan, XING Juan, LI Guang-zhong, HUA Gui-yuan, ZHAN Libo, YAN Peng

College Physics. 2021, 40(4):  32-36.  doi:10. 16854 / j. cnki. 1000-0712. 200276

Abstract ( 1488 )   PDF (353KB) ( 679 )  

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With the change of social demand for talents，many colleges and universities revise the

talent train- ing program in combination with the professional competence training. The changes

of class hours and learning situ- ation make it difficult for the traditional physics teaching mode in university to effectively guarantee the quality of talent cultivation. In this paper，in view of the existing problems in teaching，the PAD ( Presentation-Assimilation

-Discussion) Class teaching mode is used to reform the teaching of college physics course and a number of teaching

measures is proposed，involving course content，learning objectives，teaching activities，teaching evaluation，etc.

A questionnaire is employed to evaluate the teaching effect. A follow-up reform scheme is also proposed according to the teaching reflection.

Thinking and practice of ideological and political construction of electrodynamics course

LIU Xiao-jun, ZHANG Xin-yue

College Physics. 2021, 40(4):  37-39.  doi:10. 16854 / j. cnki. 1000-0712. 200251

Abstract ( 2206 )   PDF (120KB) ( 542 )  

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At present carrying out the ideological and political construction of professional

courses is an impor- tant research problem in education field. In this paper，the

electrodynamics course in physics major is combined with the research and the practice of

ideological and political courses construction. The contents and characteristics of this course

are organically combined，and the elements and some entry points of ideological and

political con- struction of courses are deeply excavated. Through teaching practice，some

preliminary effects are obtained which should play an active role in learning and promoting the

ideological and political construction of science courses. It can make the curriculum education

realize and also uses the course to its full play. At last，some summary and prospect

are put forward.

The exploration of ideological and political teaching in the course of the history and methodology of physics

ZHANG Xiao-lei, ZHANG Le, ZHANG Yu-yi, BIAN Ya-jie, YIN Ya-ling

College Physics. 2021, 40(4):  40-44.  doi:10. 16854 / j. cnki. 1000-0712. 200340

Abstract ( 2083 )   PDF (207KB) ( 368 )  

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In this paper，the course of the History and Methodology of Physics in East China Normal

Universi- ty is taken as a research object. Based on the integration of science and

humanities，the fundamental task of strengthening morality education is expected to be realized

and the targets of imparting professional knowledge，re- solving doubts，propagating the doctrine and

educating people is met by applying ideological and political ideas to traditional classroom

teaching. What studied in this paper could have a certain reference value for the science

de- partments in university to carry out the construction of course-based ideological and political

education.

Construction and practice of college physics course under the background of new engineering

WANG Xiao-ou, ZHANG Ling-li, YUAN Cheng-xun, WANG Xian-jie, JIN Chen-fei, ZHANG Yu

College Physics. 2021, 40(4):  45.  doi:10. 16854 / j. cnki. 1000-0712. 200412

Abstract ( 1977 )   PDF (837KB) ( 1038 )  

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As an important basic course for engineering specialty，college physics plays an

irreplaceable role in the development of new engineering education and the cultivation of

interdisciplinary talents with international competitiveness. In the autumn of 2018，the physics

teaching and research office of Harbin institute of technology had carried out a comprehensive

and in-depth reform on the curriculum system，teaching content，teaching mode and other

aspects in accordance with the new requirements of talent training for new engineering

construction. After nearly two years of teaching practice，good results have been achieved.

Visualized teaching of college physics based on modern information technology

QIN Fang-li

College Physics. 2021, 40(4):  50.  doi:10. 16854 / j. cnki. 1000-0712. 200200

Abstract ( 1365 )   PDF (1567KB) ( 271 )  

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Modern information technology provides many tools to realize visualized college physics

teaching. In this paper，some examples are given to show how these tools，such as numerical

simulation，mobile phone，modern intelligent equipment，animation production platform，made the

teaching of college physics visualized. The visualized teaching of college physics can improve

the students' interest in learning. This paper presents a reference for the

visualized classroom teaching of college physics.

Online teaching design and practice of college physics based on “One center，three stages，six principles and three examinations”

JIANG Hai-li, ZHAO Wen-hui, MENG Ting, ZHAO Yan-cheng, SUN Qiu-hua, LIU Yan-lei

College Physics. 2021, 40(4):  53.  doi:10. 16854 / j. cnki. 1000-0712. 200247

Abstract ( 1554 )   PDF (4105KB) ( 200 )  

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This article is aimed at the exploration and practice of online teaching design of

college physics. Rel- ying on the teaching platforms，such as Rain Classroom，Zhihuishu etc. ，the

student training process based on auton- omous learning is constructed in college physics online

course in our university. It has three stages，including preview before class，flipped classroom and

after class consolidation，and realized co-oriented education，precise teaching， gradual

progression，open discussion，independent thinking and whole-staff interaction. Furthermore，the

course is examined and promoted by platform data，supervision，students’feedback and

teachers’mutual evaluation. Over- all，the online intellectual teaching based on autonomous

learning is featured by “one center，three stages，six principles and three examinations”.

Practice results have shown that this teaching design has promoted the conver- sion from separation

to integration of in and after class teaching relying on internet information technology.

Experience summary and effect analysis ofcollege physics online teaching

XU Yi-shuang¹, WANG Gang¹, XU Jie¹, MU Chun-yan¹, LI Hui¹, YANG Guang-wu²

College Physics. 2021, 40(4):  60.  doi:10. 16854 / j. cnki. 1000-0712. 200369

Abstract ( 2390 )   PDF (1047KB) ( 1190 )  

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Based on the modularity idea，teaching links are designed in seven steps to strengthen

classroom in- teraction，the cultivation of students' ability to apply knowledge，and ideological and

political education. The com- bination of Tencent Classroom and Cloud Class is used for live

network teaching. Classroom management adopted multiple models，such as inviting counselors

to co-manage，introducing fault-tolerant mechanism，paying attention to students' emotional changes

and other measures to improve students' participation in the classroom. The average attendance

rate reaches 98% . The examination is based on the Super Star Learning Pass and is

conducted in the form of open-book examination with a large number of questions. By comparing

the students' scores of offline exam- ination in recent three years with that of the online

examination of this semester，it is found that the distribution of students' scores of this semester

is more reasonable，which indicates that online teaching has certain advantages.

The motion equation，period and position probability distribution of three-line pendulum

WU Ming-jue, WANG Shun-yu, LI Jun, XIA Xue-lian, ZHANG Li-hua

College Physics. 2021, 40(4):  64.  doi:10. 16854 / j. cnki. 1000-0712. 200296

Abstract ( 3970 )   PDF (434KB) ( 2014 )  

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In this paper，based on the Lagrange equation of conservative system，the

　　differential equation of three-line pendulum in large swing angle motion and the

　　approximate treatment method of linear vibration with small swing angle are given. Under

　　the approximate condition about the structural dimensions of the three-line pen- dulum，the motion

　　differential equation，period and position probability density distribution of the three-line

　　pen- dulum under two different conditions of large swing angle and small swing angle are discussed.

A stochastic dynamics model for the directional transport of kinesin

YANG Zi-bei, QIU Xing, CHEN Qiao-ni, WANG Hai-yan

College Physics. 2021, 40(4):  68.  doi:10. 16854 / j. cnki. 1000-0712. 200244

Abstract ( 1544 )   PDF (650KB) ( 498 )  

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In this paper，we consider the chemical-mechanical coupling of the kinesin in an

asymmetric peri- odic potential during stepping. Based on Brownian motor theory，we numerically

simulate the motion characteristics of kinesin under certain experimental conditions by MATLAB.

Firstly，we simulate the image of the displacement and velocity changing with time of a

single kinesin. Then we respectively calculate the average speed of several ki- nesin. Finally we

calculate the ensemble average of the speed of kinesin under different loads. The simulation

re- sults show that kinesin has waiting state and walking state in directional motion，the walking

step is about 8. 2 nm， and the motion has certain randomness. Comparing with the experimental

results，it is found that the calculated re- sults of the model are in good agreement with the

experimental results.

Exploration of the deceleration process of gyroscope in magnetic field starting from a simple model

FENG Xin, FAN Hong-jie, CHENG Yu-kun, ZHAO Wei, TAO Xiao-ping, PU Qi-rong, ZHAO Xia, ZHANG Zeng-ming

College Physics. 2021, 40(4):  72.  doi:10. 16854 / j. cnki. 1000-0712. 200254

Abstract ( 1512 )   PDF (1763KB) ( 765 )  

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The 12th problem of 2019 China Undergraduate Physics Tournament ( CUPT) was to study the de- celeration of a gyroscope made of nonferromagnetic conductor materials when placed in a magnetic field. There is no specific parameter to be qualified in the question，which is difficult to be solved comprehensively and uniformly by Maxwell’s equation. Starting from the infinite long conductor cylindrical model in this paper，the formulae of elec- tromagnetic resistance moment depends on magnetic induction strength，angular velocity，conductivity，and other parameters are obtained. The deriving process of these formulae is going under the condition that the direction

of the magnetic field is vertical or parallel to the gyroscope’s shaft with reasonable

approximation. Then the general rela- tion of gyroscope deceleration damping coefficient is given

when the direction of the magnetic field is relative to any

direction of the gyroscope’s shaft with the rationality verified through the dimensional analysis.

In the experimental part，an experimental facility driven by a DC motor is designed，and the

analysis of measurement data shows that the formulae of the electromagnetic resistance moment

obtained from the basic model can describe the actual gyro- scope deceleration process more

accurately.

Simulation and research on thermal lens effect of low power laser

GUO Zheng-xin¹, GAO Qi-ni¹, FAN Zi-ping¹, CHEN Qing-nan¹,

College Physics. 2021, 40(4):  79.  doi:10. 16854 / j. cnki. 1000-0712. 200306

Abstract ( 1151 )   PDF (1647KB) ( 156 )  

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Comparing with high-power laser，low-power laser is safer and its thermal lens effect is

more sen- sitive to the change of laser power，so it is more suitable for experimental teaching. In

this paper，the thermal lens effect of low-power laser is simulated by using the finite element

method，namely，the temperature field of the me- dium and the focal length of the equivalent thermal

lens are simulated，and the relationship between the focal length of low-power laser and the laser

power as well as the thermal absorption rate and thickness of the medium is quanti- tatively

explored. The simulation results are in good agreement with the experimental data，which provides a

theo- retical basis for exploring the thermal lensing effect of low-power laser.