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- Research on blended learning strategies ———taking the teaching during COVID-19 quarantine period as an example
- WANG Zu-yuan, ZHANG Rui, ZHANG Zhi-hua
- College Physics. 2020, 39(9): 1-5. doi:10.16854 /j.cnki.1000-0712.200162
- Abstract ( 1613 ) PDF (921KB) ( 821 )
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- A brief analysis of different form of Pauli-Fierz Hamiltonian in non-relativistic limit
- ZHANG Jun, ZHU Zhan-wu, HE Ze-dong
- College Physics. 2020, 39(9): 6-8. doi:10.16854 /j.cnki.1000-0712.190536
- Abstract ( 1555 ) PDF (213KB) ( 727 )
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- An analysis of the key points of wave problems in College Physics
- LI Jun, QIAN Cheng-yi, MA Mo-nan, YUAN Cheng-xun, MENG Qing-xin,
- College Physics. 2020, 39(9): 9-16. doi:10.16854 /j.cnki.1000-0712.190550
- Abstract ( 2148 ) PDF (3134KB) ( 545 )
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- Proof of the relationship between the shape of the spherical droplet surface and the principle of free energy minimization
- JIN Kang, WANG Xin-yi, GUI Kai-hang
- College Physics. 2020, 39(9): 17-22. doi:10.16854 /j.cnki.1000-0712.190512
- Abstract ( 1302 ) PDF (1375KB) ( 656 )
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- Physical distribution mechanism of the power supply
- YIN Hai-feng, ZENG Chun-hua
- College Physics. 2020, 39(9): 23-26. doi:10.16854 /j.cnki.1000-0712.190415
- Abstract ( 1061 ) PDF (461KB) ( 662 )
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- Agrange density，motion equation and continuous equation of relativistic fluid
- LIANG Gui-xiong
- College Physics. 2020, 39(9): 27-30. doi:10.16854 /j.cnki.1000-0712.190307
- Abstract ( 1895 ) PDF (174KB) ( 522 )
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- Infinite sum and residue theorem
- QIU Wei-gang
- College Physics. 2020, 39(9): 31-33. doi:10.16854 /j.cnki.1000-0712.190431
- Abstract ( 1641 ) PDF (146KB) ( 685 )
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- High-frequency resistance of metal and the method of its measurement and correction
- ZHOU Rong-hao, YANG Yong, ZHANG Qing, TIAN Fa-bao
- College Physics. 2020, 39(9): 34-40. doi:10.16854 /j.cnki.1000-0712.200001
- Abstract ( 1200 ) PDF (1065KB) ( 644 )
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- Study on the phenomenon of star-burst
- WANG Ying, ZHOU Yu-han, XIA Wang-suo
- College Physics. 2020, 39(9): 41-46. doi:10.16854 /j.cnki.1000-0712.190476
- Abstract ( 2019 ) PDF (1618KB) ( 745 )
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- Some thoughts regarding physics experimental courses at medical college based on student-centered teaching
- LI Hui, WANG Chun-feng, SUN Da-gong, KA Wei-bo, YUAN Gui-hong, ZHANG Si-qing, GAO Song
- College Physics. 2020, 39(9): 47-50. doi:10.16854 /j.cnki.1000-0712.190573
- Abstract ( 1074 ) PDF (413KB) ( 312 )
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- Mean relative speed between different molecules in mixed gases
- HAI Wen-long, PANG Dan-yang,
- College Physics. 2020, 39(9): 51-52. doi:10.16854 /j.cnki.1000-0712.200041
- Abstract ( 1659 ) PDF (152KB) ( 451 )
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- Theoretical calculation and experiment of linear expansion coefficient of metal
- LIU Jin, ZHANG Meng, LUO Duan-bin
- College Physics. 2020, 39(9): 53-58. doi:10.16854 /j.cnki.1000-0712.200085
- Abstract ( 1807 ) PDF (867KB) ( 487 )
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- Research on using mirror image method to solve the electric field of spherical projection on the plane
- ZHAN Yan, LIU Jin, CHANG Yue-yue, WANG Wen-jing, ZHANG Xian-mei
- College Physics. 2020, 39(9): 59-65. doi:10.16854 /j.cnki.1000-0712.200019
- Abstract ( 1700 ) PDF (2280KB) ( 490 )
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- Symmetry of electromagnetic field，magnetic charge and magnetic monopole: An example of symmetry analysis in teaching collage electrodynamics
- YUAN Ming-yue, LI Tong, HUANG Xiao-yan, LIN Fang, ZHANG Zhi-you,
- College Physics. 2020, 39(9): 66-71. doi:10.16854 /j.cnki.1000-0712.190486
- Abstract ( 1638 ) PDF (320KB) ( 905 )
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- Simulation and visualization of electrostatic field and electric charge movement based on Vpython
- WANG Yao, LIU Yu-ying, ZHU Shi-qiu
- College Physics. 2020, 39(9): 72-77. doi:10.16854 /j.cnki.1000-0712.190463
- Abstract ( 1707 ) PDF (1475KB) ( 1138 )
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Based on the experience on blended learning of University Physics and the
observation of teaching

activity during COVID-19 quarantine period，the characteristics and the learning achievement of blended learning

in different modes are analyzed. The common problems in online learning and blended learning are discussed，and

some suggestions on blended learning in COVID-19 quarantine period are also presented.

When we discuss the interaction of atoms or molecules with quantized
electromagnetic waves ( photons)
，the Hamiltonian in length gauge takes the advantage by replacing the
vector potential A by electric filed multiplying
the dipole. However，formulas in different papers seem to have different
forms. In this paper，we start from
Pauli-Fierz Hamiltonian in velocity gauge and obtain the length gauge
Hamiltonian in coordinate and momentum
representation，respectively，which proves the equivalence between different
forms. We hope this could help
students to understand the Hamiltonian in different forms.

The wave constitutes an indispensable part in College Physics. It is not only
the extension of electromagnetic
wave，but also the basis of optics and quantum mechanics. Students need to
work hard on wave problems.
In this paper，by investigating the students in Harbin Institute of
Technology，four key points in wave problem are
put forward，the key elements are analyzed，and some solutions are provided
to help the students to understand
these key points.

The surface shape of the droplets in the vacuum is determined by the principle
of surface free energy
minimization. In the case of ignoring droplet gravity，the minimum free
energy corresponds to the minimum surfacearea of the droplet. We derive the equations satisfied by the minimum
surface under fixed volume constraints，and use the linearized iterative method to numerically solve the equation
to prove that the surface is spherical. In addition，we prove that if the final thickness of the super-spreading liquid film is
constant，the liquid film spreading shape is also determined by the principle of minimum free energy，and its
shape is circular.

This paper mainly analyses a linear circuit with two power sources. There are
three types of this circuit:
the current - controlled dual - port network，voltage - controlled dual -
port network and hybrid dual - port
network. A dual-port network VCR can be obtained by measuring and other
methods. The physical distribution of
each part of the power of two power sources can be obtained when the VCR of
two-port network is known. The power
of each power supply consists of two parts. One part is equal to the power
provided by the power supply when it is
connected to the circuit separately. Another part is the increased power
due to the interaction between the two power
sources when they are both connected to the circuit. The increased power
depends on two power sources and circuit
parameters. According to the reciprocity theorem，when there is no
controlled source，for current-controlled twoport
networks and voltage-controlled two-port networks，the increased power of
each power source due to interaction

is equal. That is to say，the increased loss power of the circuit is shared equally by the two power sources. For a hybrid dual-port network，when there is no controlled source，the increased absorption power of one power source is equal to the increased supply power of another power source due to the interaction. The sum of the power of both power supplies is equal to the sum of the power of both power supplies when it is connected to the circuit separately. In this case，the effect of interaction is that one power source charges another power source. The results of this study are universal. It can help one to solve the power source problem of power grid，and can also solve the power source problem of other electronic circuits.

Under reasonable assumptions，this paper presents a Lagrangian density of
relativistic fluid from the
energy-momentum tensor of the relativistic fluid，and presents the equation
of motion for relativistic fluid based on
the Lagrangian density and the principle of least action. In the limit of
low speed and low pressure our equations of
motion reduces to Navier-Stokes equations. The continuity equation of fluid
is also discussed. It is found that the
continuity equation of fluid in Newtonian mechanics can be established only
when the influence of pressure and external
force can be neglected，even at the low speed of flat space-time.

The contour integral of a complex function on an infinite square is
approximately the same as another

complex function. The analytical expression of infinite summation of all the zeroes of some transcendental equation is

derived by residue theorem，which is verified by the numerical calculation.

Resistance is an important physical parameter of metal materials. The
measurement of high-frequencyresistance is affected by the skin effect， the
distributed inductance and the capacitance. Rare special experimental
measurement is reported about it. In this paper， in the condition that the
test objects can be actively changed and the
metal filaments are used for the experimental measurement， the
high-frequency resistance measurement can better
suppress the skin effect. Meanwhile，by analyzing the resistance， inductance
and capacitance equivalent circuits of
the fixed-shape non-ferromagnetic metal filament samples， the vector
voltage analysis data is obtained by a frequency-sweeping phase-locked amplifier. The method of optimal matching is used to
successfully modify the influence
of the high -frequency distributed inductance and capacitance on the high
-frequency resistance measurement of
metals from the perspective of engineering practice. An improved method for
high - frequency resistance
measurement of ferromagnetic metals is also proposed. The electrical
conductivity of the metal remained unchanged
at high frequency，which is consistent with the theoretical analysis
results. This study provides measurement ideas for
higher frequency resistance，and has also significance for improving
electromagnetic nondestructive testing and electromagnetic
compatibility research and design.

In this paper， the interesting phenomenon of star-burst ( which arose from the
pictures taken from bulbs at night) is investigated theoretically and
experimentally. Through properly simplifying the physical model of
photographing process， the star-burst is analyzed theoretically depending
on Francophile diffraction theory，with the
influencing factors including the aperture shape，aperture size， incident
wavelength and camera distance，etc. Then
the influencing factors for star-burst has been systematically studied
through contrast experiments. Further comparison
on the results got from theoretical and experimental methods has been
methodically carried out. Finally，advice
for how to obtain obvious star-burst is given.

Teaching reform in regards to teaching content and method has been conducted
for physics experiment
course in the Peking University Health Science Center for more than ten
years. The fundamental physics，medical application and modern technologyare emphasized in physics
experiment course. A deep investigation for
the student !s opinion on the physics experiment course is also carried
out. A comprehensive thoughts are presented

with regard to the results of the investigation.The results obtained in this study should provide reference for future teaching reform.

Based on the definition of the relative speed， the mean relative speed between
different molecules in
mixed gasses is derived by the combination of Maxwell speed and velocity
distributions.

In this paper，the coefficient of thermal expansion of aluminum and copper
metals is obtained by
calculating the lattice constants，binding energy and Debye temperature via
the density functional method based on
quantum mechanics. Experimental design and data measurement are also
carried out. Moreover，the theoretical simulation
values are compared with the experimental results achieved by using an
optical lever. The error sources were
analyzed and the experimental methods for improving the errors were
proposed. The results should provide reference
for the future experimental design and theoretical simulation of metal
thermal expansion coefficient in university
physics courses.

The mirror image method can be used to solve the electrostatic field in the
system with high symmetry.
This paper discusses a model in which there is a circular projection on the
plane of an infinite grounded conductor，
and the point charge is located on the axis of symmetry of the system and
has no contact with the surface of the
conductor. Through the discussion on the relations among the radius of the
circle，the distance between the center of
the circle and the plane，and the shortest distance between the charge and
the dome，three convergent models are
summarized. In the first two cases，no matter where the point charge is，a
stable solution can always be obtained，
and the spatial electric field distribution is given by combining with
MATLAB simulation. The latter case cannot be
solved by the mirror image method，which reflects the limitations of the
mirror image method.

Symmetry plays great importance role in modern physics. The symmetry analysis in
electrodynamics
is not only useful for solving specific excises，but can also provide us
profound understanding of basic concepts.In
this paper，we briefly summarize the general symmetry properties of
electromagnetic fields in its non-relativity form.
We address that gauge invariance is the fundamental symmetry classic
electromagnetic field and governs the electromagnetic
interaction. The broken of duality in electromagnetic field is an example
of this governance. Based on these
understanding，two confusing concepts，that magnetic charge and magnetic
monopole，are further discussed.

Based on Coulomb’s law and superposition principle of electric field，this paper explores the electrostatic field of point charge and charge system. With the help of computer software VPython，the electrostatic field under various charge distributions is simulated. Data analysis is carried out by Plotly software. In addition，we study the trajectory and energy characteristics of charged particles in the electrostatic field. Also，we visualize electric dipole’s three-dimensionalmotion in the electrostatic field in real-time. Teaching practice indicated that: thesimulating and visualizing electrostatic field and charge movement based on VPython andPlotlyenables students to have a better understanding of electrostatics-related knowledge，which is a useful supplement to the classic physics teaching.