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Table of Content
15 November 2024 Volume 43 Issue 10
β-γ Coincidence Measurement experiment based on Pixie-Net digitizer
YAN Zhou, LOU Jian-ling, ZHANG Si-yang, ZHANG Ji-zhi
College Physics. 2024, 43(10): 3. doi:
10.16854/j.cnki.1000-0712.240068
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We attempt to use the Pixie-Net digitizer for the β-γ coincidence experiment in order to replaces complex traditional electronics and then to simplify experimental equipment. The measurement results show that the relative error between the measured activitivity using the Pixie-Net digitizer and the theoretical value is less than 5%, which is much better than the results with traditional electronics. It is feasible to replace traditional electronic instrument devices by the Pixie-Net digitizer.
The graceful Dirac function
YANG Shi-jie
College Physics. 2024, 43(10): 10. doi:
10.16854 /j.cnki.1000-0712.240035
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110
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Starting from Dirac's δ-function, we derive the sum rule of the spherical hamonics. We obtain a generalized y-transform which covers several traditional integral transformations. We also construct a new type of integral transformation and its inverse transformation. Furthermore, we introduce the Schrdingers equation by making use of the Dirac function, which effectively avoid the plane wave hypothesis for a quantum particle moving in an external potential. The de Broglie matter wave relations are naturally derived via dimension analysis. Our method provides a new point of view to understanding quantum mechanics for students.
Modification of transition rate by higher order time-dependent perturbation#br# #br#
LI Hai-feng, OU Zhi-min, ZHANG Kai-feng, HUANG Yan
College Physics. 2024, 43(10): 21. doi:
10.16854 /j.cnki.1000-0712.230235
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Quantum mechanics is a physical theory which describes the behavior of microscopic matter. Moreover, it is the foundation of many physical branches. In fact, under the influence of external time-dependent perturbation, microscopic particles can undergo quantum transitions between different stationary states, which has attracted great research interest. According to time-dependent perturbation theory, the probability of microscopic particles transitioning from one stationary state to another per unit time is called the transition rate. For the constant perturbation, transition rate formula derived by the first-order perturbation approximation is time independent, which is the so-called Fermis golden rule and is widely used in theoretical research in physics, chemistry, biology, and other disciplines, especially in the field of quantitative computing. In traditional quantum mechanics text books, the high-order perturbation corrections are often ignored, and the transition probability or transition rate is derived by the low-order perturbation approximation. In the multi-levels systems, if the first-order perturbation is zero, or the Fermi golden rule is no longer applicable. For this complex situation, it is necessary to go beyond the Fermis golden rule and consider the impact of high-order time-dependent perturbation on the transition rate. On the basis of the time-dependent perturbation theory, both constant perturbation and periodic time-dependent perturbation are considered in this paper and the influence of high-order correction terms on the transition rate is attained. Furthermore, it is shown that intermediate states which satisfy certain conditions between the initial and final states can have an impact on the transition rate when the high-order perturbation approximation are considered. Therefore, the results can reflect the actual quantum transition process more comprehensively.
Angular momentum theorem in a non-centroid system#br# #br#
Han Wei-hua, Liu Qing-fang, Wang Jian-bo, Wang Li
College Physics. 2024, 43(10): 26. doi:
10.16854/j.cnki.1000-0712.230443
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Choosing an appropriate reference point is crucial in solving rigid body motion problems, effectively simplifying the problem-solving process. In comparison to the center of mass axis, a non-centroid axis of rotation provides a more flexible perspective. This paper, by deriving the angular momentum theorem in a non-centroid system and using the example of a ball colliding with a free rod, illustrates its practical application in real-world scenarios. The paper offers readers a novel approach to addressing rigid body motion problems, particularly providing intuitive insights in complex situations.
Theoretical study on the influence of cathode radius on the measurement of#br# electron chargetomass ratio using magnetron#br#
SU Ya-feng1, CHEN He-sheng2, ZHANG Jun-wu1, ZHANG Pei1
College Physics. 2024, 43(10): 30. doi:
10.16854/j.cnki.1000-0712.230417
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55
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The dynamic equation of electron in the experiment of measuring chargemass ratio of electron by magnetic control method is analyzed, and the theoretical calculation formula of measuring the chargemass ratio of electron by magnetic control method is given. The electron trajectories are further simulated by using the dynamic equation. The calculation results show that under the condition of nonzero cathode radius, electron motion exhibits a kind of periodic motion such as alternating curve of many rotating heartshaped lines. By means of simulation calculation, it is verified that the theoretical formula obtained by us is basically consistent with the experimental results of dynamic equation simulation, thus verifying that the theoretical formula given is correct and universal.
Are the electric and magnetic fields of plane electromagnetic #br# wave in free space always in phase?#br#
XIAO Chuan-yun, LIU Yu-zhen
College Physics. 2024, 43(10): 39. doi:
10.16854/j.cnki.1000-0712.240070
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65
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It is stated in nearly all textbooks that the electric and magnetic fields of any plane electromagnetic wave in free space are always in phase,no matter whether the textbooks are in Chinese or in English,whether they are College Physics,Electromagnetics,or Electrodynamics. Based on Maxwell’s equations,we prove in this paper that the above statement is actually not always correct. In general case,we can only state that the electric and magnetic fields of a plane electromagnetic wave in free space are in step,which can be in phase or out of phase,depending on the choice of coordinate systems.
Unified method for determining band bending of various #br# contacts in semiconductor physics#br#
SONG Jian-jun, TANG Ai-lan, LIU Wei-feng
College Physics. 2024, 43(10): 44. doi:
10.16854/j.cnki.1000-0712.230473
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82
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In semiconductor physics course,PN junction,gold-semi contact and MIS structure are common contact situations. However,when students learn these contact types,they often find it difficult to make a homogeneous and unified comparative analysis of these different contact types,and cannot form a unified knowledge system,which causes confusion in understanding. In this paper,a unified judgment method of energy band bending applicable to various types of contact is proposed which provides a unified statement for the energy band bending for various types of contacts from the perspective that the establishment of built-in electric field affects the potential energy of carriers and thus produces energy band bending. The formation of the built-in electric field is explained from the microscopic point of view of the carriers flow in the energy band. This judgment method can help students sort out the knowledge of various physical contacts in semiconductors so as to achieve the effect of drawing inferences in the energy band analysis learning.
The ubiquitous resistance in physics
JIN Feng-tao, GAO Cheng, WANG Xiao-wei, DAI Jia-yu
College Physics. 2024, 43(10): 50. doi:
10.16854/j.cnki.1000-0712.230459
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63
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In the study of physics,the keyword resistance can be found in many laws and phenomena. The fundamental reason for the ubiquity of resistance is that everything is a contradictory unity composed of positive and negative aspects. The stable state of things is the result of the balance between spear and shield. When the balance is disrupted,the contradiction becomes apparent and the result is that the trend of resisting state changes. Energy,momentum or matter undergoes transfer during the process of resistance. Understanding this universal principle not only makes learning more efficient and enjoyable,but also allows one to appreciate the beauty and profound meaning of physics.
Experimental data measurement system of superconducting quantum interference device#br#
BAI Zhi-ming1, FENG Ru1, LI Jian1, LI Shuo2
College Physics. 2024, 43(10): 58. doi:
10.16854 /j.cnki.1000-0712.230476
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50
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1.College of Science, Northeastern University, Shenyang 110819, China;
2. College of Information Science and Engineering, Northeastern University, Shenyang 110819, China)
Abstract:To meet the current requirements of lownoise, high precision, and high sensitivity measurements in SQUID quantum experiments, in this paper a SQUID experimental data measurement system is presented based on a singlechip STM32H750 core board and an AD8429 amplifier. By processing and analyzing the experimental curve obtained from the singlechip, the RMS noise value of superconducting quantum signal is determined to be 2.009 μV, which is close to the theoretical limit noise value. Additionally, the interference effect curve of the ringshaped liquid droplet Josephson junction is also measured by the system, in which periodicity is regular and uniform, and peaktopeak values are approximately consistent. The experimental results show that the system exhibits excellent stability and accuracy, which may lay the foundation for the development of university physics SQUID demonstration instruments.
Discussion on the teaching of electromagnetic field and wave #br# course under the background of outcome — taking electrostatic field as an example#br#
Zhang Xiao-lin
College Physics. 2024, 43(10): 63. doi:
10.16854/j.cnki.1000-0712.230406
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48
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Under the concert of student-centered and outcome-based, in this paper the teaching problem of electromagnetic field and wave course is discussed. Taking the teaching of electrostatic field as an example, the effect of order and direction is an achievable goal through hierarchical core knowledge system. The story-based guidance make abstract knowledge rely on the specific process, avoid the abrupt and boring feeling and arouse curiosity and thinking. Guided learning skills by refining the logic of knowledge with structure diagrams. Engineering cases are used in the teaching to integrating theoretical knowledge with the practical problems so that the sense of harvest is created in this way. Gradual case with gradients can break down complexity and increase student’ confidence. Finally, the use of online course classroom is discussed to continue the stimulation of students’ potentiality. This method that considers teaching from the students’ perspective improves the students’ participation and the sense of harvest, and also cultivates their potential.
A survey on the learning conception of physics lab experiments #br# of science and engineering university students#br#
Huang Le-heng1, 2, Zheng Bo-wei1, 2, Fan Bing1, 2, Xiao Yang1, 2, Xie Cui-ting1, 2, Xiong Jian-wen1, 2, Wu Xian-qiu1, 2
College Physics. 2024, 43(10): 67. doi:
10.16854/j.cnki.1000-0712.230475
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46
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In order to reveal the learning conceptions of physics lab experiments (CLPLE) held by university students majoring in science and engineering, in interviews and surveys with students from South China Normal University are conducted. The phenomenological analysis of the interview data initially revealed eleven types of progressively sophisticated CLPLE, such as memorizing and cookbook-style operating. Then the exploratory factor analysis of the survey is further verified nine types of these conceptions. This result suggests that the CLPLE held by science and engineering undergraduates constitute a hierarchical outcome space, from low to high, reflecting disciplinary knowledge orientation, disciplinary process orientation, and nature of discipline orientation, respectively. Meanwhile, compared with non-physics majors, physics majors, it is found to agree more with the CLPLE as cookbook-style operating, mastering skills and experience and verifying. It is recommended that the instruction of college physics lab experiments further coordinate the theoretical and experimental courses and underline the unique educational function of lab experiments.
Resistant-drawnforce in granular material
MEI Li-huan, TANG Chen-ran, WANG Ying, LIU Miao, GE Jian-jian
College Physics. 2024, 43(10): 74. doi:
10.16854/j.cnki.1000-712.230425
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51
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38
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Study on resistantdrawn force in granular material has important theory meaning and practical value for optimizing engineering design and guaranteeing project safe operation. In this paper, the relationships between the resistantdrawn force and the imbedded height for different pilediameters calculated from Janssen theoretic model is found to agree well with the test data.
Research on the intelligent measurement device and influencing factors #br# of ice thermal conductivity based on Arduino#br#
HU Cheng-li1, ZHAO Tian-chi1, LIU Fu-yao2
College Physics. 2024, 43(10): 78. doi:
10.16854/j.cnki.1000-0712.230469
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56
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Just Accepted
