Understand physical images and make good use of class comparison ideas

The following article comes from WeChat public account: China Physical Society Journal Network, author Qiang Yan Chen Zheng

| Author: Qiang Yan 1 Chen Zheng 2, †

(1 Peking University Affiliated Middle School)

(2 School of Physics and Engineering, Beijing Jiaotong University)

This article is selected from "Physics", No. 6, 2022

01

introduction

The birth and development of physics is a process of "starting with philatelic, finally thinking". Starting from their own sensory experience, humans observe and experiment with different types of natural phenomena. Based on this basis, the law of phenomenon is formed by summarizing and summarizing, and then further "axiom" becomes a simple, complete, and accurate theory expressed in mathematical languages. system. Through this process, the common laws behind the seemingly irrelevant appearances are revealed. Various natural phenomena finally can interpret and predict with a set of simple propositions to cooperate with logic and mathematical computing rules to achieve the "thinking economy economy ", Allowing humans to have limited memory and information processing capabilities to cope with the complicated world, this is the essence of physics [1].

However, for beginners, facing the highly abstract conclusions of physics directly, when the lack of the need to understand from the symbolic to abstract process, it will fall into the dilemma of "going to the house". High difficulty, either simply regard it as "Tianshu", or "remember" the knowledge points. This seems to get a compressed file. Although this file contains rich information, there is no corresponding decompression software. The user cannot restore the compressed file, and it cannot extract the information. Naturally, it cannot be used. As a physics teacher at the basic education stage, it provides students the necessary "decompression software" to help them understand the intermediate process and thinking tools of physics construction, so that they can truly learn and use.

02

Physical images are a bridge that is figurative and abstract

"The basic way of human cognition of nature is their own perception, of course, human physics also leaves the shadow of sensory experience everywhere" [2]. Physicists do not "change" abstract mathematical formulas out of thin air. They need auxiliary tools in the process of completing their thinking and abstraction. This is a physical image. The academic circles did not give physical images a unified and strict definition, but generally referring to a scene of a specific scene from daily life experience when people face the problems they want to study.

In the early days of physics, whether it was the planetary movement of Capeler, the slope of Galileo, the touch of the ball of Wickel, or the Newton's fluid, the interaction between the objects involved in itself and the object was The tangible object that can be seen can form direct experience of people's sensory, and these scenes form the original physical images. In -depth research on less intuitive phenomena later, often by looking for their characteristics, and then imagining it as a tangible object with similar characteristics, with the help of the pictures based on tangible objects to further think and abstract, Form the physical model describing the corresponding object. For example, the phenomenon of heat, electricity, magnetic, and other phenomena, physicists initially imagined them as a fluid like "a clear water", and then based on the sensory experience that has been established in the water and the "continuous", "conservation" summarized from it, The main nature is to propose hypothesis on heat, electricity, magnetic, etc., make predictions and pass experimental verification, and then obtain physical laws in related fields.

Although the initial image may be corrected or even abandoned with the deepening of research, physical images have undoubtedly played an important auxiliary role in the theoretical establishment process, and because many physical images are used in the field of physical branches, their theory is therefore theory. The model and mathematical expression both have extremely high communication. In -depth understanding of typical physical images, it is easy to do it when encountering related problems in different fields. Learning efficiency and ability to learn and use will be greatly improved.

03

Thermal and energy based on fluid images

Fresh science is an important physical branch that physics learners must understand. It has played an important role in the development of the first industrial revolution represented by steam engines to today. However, the concepts of temperature, internal energy, heat, entropy, etc. are very abstract, which brings great difficulties to learning. Imagine the heat as "a Wang water" and use the fluid physical image to deal with it, and it will get more effort. Looking back at the development history of thermalism, physicists do it along this thinking. In 1714, Hualun Hait improved mercury thermometer and formulated the Hua's temperature label. Thermodynamics has since embarked on the road of experimental science. At first, the theory of theory that explained the experimental phenomenon was based on fluid images. This is "theory of thermal quality": "The heat is a kind of hot -quality fluid, which can penetrate into all objects, not born or immortal; an object is cold; a cold is cold; a cold is cold; It is still hot, depending on the thermal quality it contains. "Calorie, which is still used in a certain field today, is derived from the Caloric. Sadica Kano is under the "theory of theory", and it is impossible for the famous Kano theorem based on thermal conservation (similar to the quality of the fluid) and permanent motivation based on thermal conservation (similar to the fluid quality conservation) and permanent motivation. In his own words, "We can compare the power of heat enough to the waterfall. The height of the whereabouts, that is, the temperature difference between the two objects that exchange the hot quality. "

The phenomenon of bacon is considered to be a movement from the phenomenon of friction, and the dissertation of Romonov's papers in 1746 is the performance of the molecular movement. David's ice friction melting experiment further confirmed that heat is a kind of exercise rather than thermal quality. Until Maye proposed that heat is a form of energy, Jiao Er can establish a regular contact with the heat through thermal power as the heat. The concept was gradually abandoned. However, when we use energy to describe the macro heat phenomenon, we still find that the image that it emerges in our minds is still a certain fluid. The temperature corresponds to the "water level" height, the heat corresponds to "water flow", the heat capacity is like a "one" one " "The capacity of the sink" is more than the "bottom area of ​​the sink" than the heat capacity. In this image, thermal phenomenon and life experience are so consistent, the first and second laws of thermodynamics should be clear at a glance, and the form of its mathematical model is exactly the same as the model of describing the fluid. Although the 20th -century physics research went deep into the micro field, the fluid image was replaced by a large number of ranging balls (molecular motion images) when discussing the essence of heat, and the statistical method needs to be introduced to describe the thermal nature of the object. However, simple classic thermodynamics is still the mainstream when dealing with macro heat phenomena, and fluid images still play a huge role.

04

Electricity and magnetic based on fluid image

Electromagnetics is also an important part of physics, and it is inseparable from our lives. For physics learners, it has the same problems as thermalology. It is invisible and invisible, and the concepts and laws are abstract. We can also use the same way to deal with it, and we can imagine electricity and magnetic as "water". However, the situation of electromagnetics is slightly different, and it involves several different fluids.

After the Gilbert's "Magnetic" separated the electrical and magnetic phenomenon in 1600, people regarded electricity as a fluid that carried electrical properties in the process of studying electricity. The fluid is the same. In 1729, Stephen Gray can allow these objects to attract other objects after contacting other objects by contacting the frictional glass rods, indicating that electricity can be transmitted between objects. Attributes. In 1733, the French scientist Di Fei found that the copper crumbs that had been in contact with the glass rod had rejected each other, but they attracted each other with the copper crumbs that had been contacted with the power resin, which further proposed that the electricity is two different types of fluids (dual fluids of the dual fluid (dual fluids (dual fluids (dual fluids (dual fluids Say). In 1850, Franklin replaced the bilateral theory with a single current, and the surplus of a kind of fluid was used to explain the interpretation of homosexual reprimination and the opposite sex. Although modern science proves that the carrier of electricity is derived from the basic particles in the atom, when describing a macro phenomenon, like a water flow (electrostatic) -driven current, which is like a water level height difference, is still the image we use more often. Essence

From Faraday to Maxwell's work re -unified electricity and magnetic, and finally solved most classic electromagnetic problems through the simple Maxwell equations, which also played the role of fluid images. Faraday creatively proposed the concept of "field", extending electrical and magnetic from the particles limited in the material to the space. The concepts of the language "force line" and "force tube" he described in the field were born from the problem of fluid flow. Streaming and flow pipes. On the basis of this image, Maxwell has established a precise mathematical model through analogy of electric fields, magnetic fields, and non -compressed fluids. For example, the fluid divergence of the fluid means a decrease in the flow rate, then the divergence of the power line or magnetic wire means the reduction of the strength of the electric or magnetic field; the mathematical structure of the vortex of the inductive electric field is exactly the same as that of some ideal fluid vortex. These ideas are fully reflected in his articles such as "On the Physical Power Line", "On Faraday Line" (Figure 1). The concepts such as gradients, rotations, and scatteredness commonly used today are based on Maxwell based on "mathematical classification of physical quantities" based on fluid images [3].

Figure 1 Maxwell's work "On the Phantom Line", "On Faraday Line"

05

Elasticity based on physical images

The analog method is often used in the teaching of basic physics, but it is often out of the level of intuitional analogy and flowing on problem -solving skills. For teachers with deep physical foundations, it is clear that beginners are often difficult to discover the connection. By reviewing the development of physics, it can be found that the analogy method is actually an important and underlying thinking method for physicists to carry out work. The key to this method is to understand and understand physical images. In addition to the fluid images of this article, the physical images involved in basic physics include not many types of particle images and fluctuation images. Therefore, in the process of teaching, taking specific knowledge points as an example, the corresponding physical images can be explained in order to give full play to the power of analog thinking.

references

[1] Chen Zheng, Zhang Yufeng, Wei Hongxiang. Physics, 2021, 50 (01): 54

[2] Chao Yongzhen Yilang. What is physics. Beijing: People's Posts and Telecommunications Press, 2017

[3] Theoretical concept of Malcolm Langgel. Physics. Hefei: Chinese University of Science and Technology Press, 2017

This article is authorized to reprint from WeChat public account: China Physical Society Journal Author: Qiang Yan Chen Zheng

Reprinted content only represents the author's point of view

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It does not mean the editor of the high energy institute of the Chinese Academy of Sciences: Lai Yuecheng

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