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Table of Content
20 January 2017 Volume 36 Issue 1
Discussion on beginning teaching of mechanics from established calculus
BAO Jing-dong
College Physics. 2017, 36(1): 1-3. doi:
10. 16854 /j. cnki. 1000-0712. 2017. 01. 001
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1338
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Starting from introducing the contributions of Newton and Leibniz for established calculus，we discuss the motivation of limitation and derivative. Through analyzing an example of“calculating both velocity and acceleration of a boat moved by equal speed”，the coordinate system，vector and differentiation are applied comprehensively. This makes students understand deeply the motion law of a particle and physical requirement of vector projection.
Physical cognition and discussion on the equal time commutation relation of a free real scalar field system under box normalization
SUN Wei-min
College Physics. 2017, 36(1): 4-7. doi:
10. 16854 /j. cnki. 1000-0712. 2017. 01. 002
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1673
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The equal - time commutation relation of a free real scalar field system under box normalization is discussed. It is found that according to the usual particle interpretation of a free field theory， the equal - time commutation relation of a free real scalar field system， in the sense of natural mathematics，should use some periodically continued Dirac delta function to replace the usual Dirac delta function. Mathematically，this is both natural and necessary，and the equal - time commutation relation of a free real scalar field could naturally revert to the original standard form in the infinite volume limit. This paper gives detailed discussion and demonstration for this fact，and from the angle of physics makes some speculative analysis for the physical essence of the box normalization treatment in field theory，as well as gives some fundamental cognition.
An example of research on physics by analogy method
YU Feng-jun
College Physics. 2017, 36(1): 8-9. doi:
10. 16854 /j. cnki. 1000-0712. 2017. 01. 003
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1356
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740
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The function of analogy method in physics teaching is explained by using an example of deriving gravity field distribution on the surface of the earth.
The equilibrium configuration of charged rope around charge system
QIU Wei-gang
College Physics. 2017, 36(1): 10-11. doi:
10. 16854 /j. cnki. 1000-0712. 2017. 01. 004
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1329
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459
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The equilibrium differential equation of charged rope around charge system is derived. The numerical solution shows that the configuration may take convex curve，peanut curve and multi - layer knots with different parameters.
Analysis and calculation of water pipe problem
WANG Jian-wei
College Physics. 2017, 36(1): 12-14. doi:
10. 16854 /j. cnki. 1000-0712. 2017. 01. 005
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1298
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659
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There is a class of problems in mathematics called the problem of the water pipe. The flow rate of the inlet pipe and the drain pipe being constants are not the case. By using the Bernoulli equation in fluid mechanics，we calculate drainage pipe flow along the variation of the water level of the pool and discuss in the inlet and outlet pipe being opened at the same time the conditions，the pool filled with water，and can not be filled with water conditions. The scientific errors in this kind of problem are corrected.
Space magnetic field of rotating disc with charge at constant angular speed
WANG Shu-ping，FAN Hong，ZHANG Li-gang
College Physics. 2017, 36(1): 15-18. doi:
10.16854 /j.cnki.1000-0712.2017.01.006
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1470
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By solving Laplace equation of several areas in spherical coordinates，we get scalar magnetic potential and magnetic field distribution that produced by a rotating charged body at constant angular speed. Then the magnetic strength of the rotating disc’s center，the rotating disc’s axis，the rotating disc’s far field and near region are obtained.
The law of refraction in absorbing medium
ZHANG Jing，WANG Hai，LIU Shu-yong
College Physics. 2017, 36(1): 19-21. doi:
10.16854 /j.cnki.1000-0712.2017.01.007
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1894
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In an isotropic non-absorbing medium， light propagates without the amplitude attenuation and refracts at the interface of two media obeying Snell’s law with real numbers. However， light travels in a homogeneous absorption medium with not only the attenuation of amplitude along the direction of propagation，but also the separation between equi-amplitude and equi-phase surfaces. Considering these phenomena， this work reviews the concept of the complex refractive index and Snell’s law with complex indexes. Then two typical cases are discussed，namely， light incident from an absorbing medium to an absorbing medium，and light incident from a non-absorbing medium to an absorbing medium，by which the necessity and convenience of Snell’s law with complex indexes are demonstrated. The relationship between Snell’s law with real form and Snell’s law with complex form is also clarified.
The air-based instrument of measuring Young’s module by stretching
ZHAN Li-bo，LI Guang-zhong，WANG Yun-chuang，QIN Dan，XING juan，LIU Jun-ying
College Physics. 2017, 36(1): 22-24. doi:
10.16854 /j.cnki.1000-0712.2017.01.008
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714
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In this paper，we give air - based designs on the experiment of measuring Young’s module by stretching. We replace standard weights with air-driven equipment. The air-based instrument can stop shaking of metal wire，and the experimenter can select the size of tension accurately and continuously in the experiment. In this way， the experimenter can measure the Young’s modulus of metal wire accurately. Another， the air - based instrument can avoid weight hurt students. The air-based instrument of measuring Young’s module by stretching can effectively solve the difficulties in the traditional experiment and meet the learning needs of students.
Determination of metal linear expansion coefficient based on BOS-PSD0018
TANG Xin-ling，LIU Zhi-zhuang，ZHANG Wen-zhao
College Physics. 2017, 36(1): 25-27. doi:
10.16854 /j.cnki.1000-0712.2017.01.009
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1269
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371
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In order to improve measurement precision and sensitivity of metal linear expansion coefficient，thus simplify digital measurement and computer processing，the micrometric displacement is completed by using the core element of PSD photoelectric sensor. An optical enlargement device is employed to advance micromovement resolution ratio. The chip BOS-PSD0018 is employed to achieve micromovement conversion. A microprocessor is utilized to realize digital procession and display for metal linear expansion coefficient. The standardization test is completed by using a copper rod; the detection test is conducted by using iron rod. The results show that the maximum relative error of metal linear expansion coefficient is less than ±2. 3%，the optical enlargement device can increase 4 times for the resolution ratio of micromovement.
Adopting semiconductor laser for measuring the Planck constant
SUN Zheng-he，LU Te-an，LIU Tian-yu，LONG Yong-ji
College Physics. 2017, 36(1): 28-32. doi:
10.16854 /j.cnki.1000-0712.2017.01.010
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1375
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980
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An experimental method of small semiconductor laser weak light source for measuring the Planck constant based on the photoelectric effect is adopted. It has the advantages of high precision， small volume， light weight， low cost， save electricity，convenient. It has been demonstrated that the semiconductor laser light source has a good monochromaticity compared with the related other light source by the spectral analysis. The reasons of influencing the measurement accuracy because of the monochromatic spectral line width are analyzed theoretically.
Estimating mass of globular cluster using the virial theorem
GAO Xin-hua，XU Shou-kun
College Physics. 2017, 36(1): 33-36. doi:
10.16854 /j.cnki.1000-0712.2017.01.011
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1824
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The virial theorem can be used to analyze the kinetic and potential energy of N-body gravitating system，which is widely used in astrophysics. Globular clusters have reached dynamical equilibrium through long-term two-body relaxation. We estimate the dynamical masses of four globular clusters NGC 1851，NGC 1904， NGC 7099 and NGC 5964 based on high-precision radial velocities and the virial theorem. The dynamical masses of the four clusters are 0. 99×10
5
M⊙ ，0 . 54×10
5
M⊙ ，0. 44×10
5
M⊙ and 4. 88×10
5
M⊙ ，respectively.
Basic principles of magnetic levitation and overview on their implements
DONG Jin-wen，ZHANG Kun-lun， JING Yong-zhi
College Physics. 2017, 36(1): 37-40. doi:
10.16854 /j.cnki.1000-0712.2017.01.012
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1578
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1105
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Earnshow theorem and Braunbeck idea are two basic principles of magnetic levitation system. Their contents and scope of application are introduced.The prime stability judgment of magnetic levitation system from the basic principles is listed. According to this judgment，eight kinds of magnetic levitation systems are discussed which are classified by implement materials，physical principles and characteristic. Finally it is pointed out that each kind of magnetic levitation system has different value and prospect in application.
A quantitative comparison on the difficulty degree of Chinese and American physics textbook of university
LI Xiao-mei， LI Chun-mi，SUN Hui-juan
College Physics. 2017, 36(1): 45-48. doi:
10.16854 /j.cnki.1000-0712.2017.01.013
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1565
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953
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Two popular textbooks from China and America are chosen to analysis，and the comparative index system concluding the breadth and depth dimensions is built. The main conclusion is that the breadth and depth of knowledge of the textbook in China is lower than the United States ones，but students feel the textbook of China more difficult due to its highly demand of abstract mathematics. This model can be used for both qualitative and quantitative analysis，and also it can be used well as the tools for the comparison of international textbooks.
Design of college physics problems based on Marzano’s taxonomy of educational objectives
XIE Li，LI Chun-mi，XU Da-hai
College Physics. 2017, 36(1): 45-48. doi:
10.16854 /j.cnki.1000-0712.2017.01.014
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821
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614
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Based on Marzano’s taxonomy of educational objectives，the two-dimensional framework of physics problems is built. This framework has two domains of knowledge ( information and mental procedures) as one dimension and cognitive process ( retrieval， comprehension， analysis and knowledge utilization ) as another dimension. According to the dynamic relationship between the two dimensions，physics problems designed from the low level to high level in cognitive process and from information to mental procedures are classified into 4 levels and 13 sublevels with specific examples offered.
Influence of mass of cone spring on oscillatory period
ZHANG Jing-xin，HOU Can，ZHANG Feng
College Physics. 2017, 36(1): 49-51. doi:
10.16854 /j.cnki.1000-0712.2017.01.015
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1193
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Considering the mass of the spring itself，an energy method is adopted to analyze the total kinetic energy of the truncated cone-shaped spring system.An accurate expression of the effective mass coefficient is derived by introducing the shape function.And the range of the effective mass coeffiicient is between 1 /5 and 8 /15.
The friction measurement device based on micro control unit
CHEN Fei，SUN Chang-ping，CUI Bao-feng，LU Bao-feng
College Physics. 2017, 36(1): 52-55. doi:
10.16845 /j.cnki.1000-0712.2017.01.016
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1263
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1114
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Based on micro control unit，a new type of sliding friction force measurement device is designed by using techniques of resistance strain sensor，ultrasonic velocity detecting，wireless transmission，LCD screen showing，DC acceleration and deceleration motor，etc. In comparison with the traditional experimental measurement of sliding friction force， the present device has the advantages of the convenient operation，high measuring accuracy， visual phenomenon，beautiful appearance，wide application prospect，etc. It can not only be used as teaching aid in the classroom demonstration，but also provide the references and thoughts of the smoothness determination of products， material friction coefficient measurement，etc. in the enterprise.
The semi-quantitative estimation of the tropospheric temperature profile
FU Xin-chuan，DAI Xin，YANG Chuan-dong，LU Jin-shuai，TAO Zong-ming
College Physics. 2017, 36(1): 56-59. doi:
10.16854 /j.cnki.1000-0712.2017.01.017
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1197
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1021
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In general， there is an example of estimating the surface temperature in the quantum physics part of college physics，however，can this method be extended to estimate the tropospheric temperature profile? In this paper， the earth and multi-layer model of troposphere is established; according to the latest atmospheric absorption and radiation constant， the related parameters of multi - layer model of troposphere are calculated; using the radiation energy balance and Stefan - Boltzmann law，the tropospheric temperature profile is estimated. The calculated results show that in 5 - layers model of the troposphere， the estimated surface temperature and the tropospheric temperature profile are in well agreement with the actual surface average temperature and the tropospheric temperature lowered ratio 6.5K/km under the standard atmosphere model.
Monitor the terrestrial magnetic field horizontal component in real time by mechanics and optics techniques
SUN Jie，WANG Yan-zhao，ZHANG Zhen，ZHANG Ya-nan
College Physics. 2017, 36(1): 60-64. doi:
10.16854 /j.cnki.1000-0712.2017.01.018
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987
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We design a device system to measure the terrestrial magnetic field horizontal component by using mechanics and optics techniques. A coil will be in the situation of simple harmonic vibration under the action of torsional moment and magnetic moment. The relative distance between the two equilibrium position and the period of the simple harmonic vibration is measured. Then the terrestrial magnetic field horizontal component is calculated. This device has advantages of simply structure， flexible operation，and accurate results. Moreover， it can achieve the dynamic real-time monitor.
College Physics. 2017, 36(1): 65.
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636
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257
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