Keywords: physical concepts, establishing ideal models, doing more exercises and paying attention to * * *
Introduction: Physical concept is the basic component of physical knowledge system. If we want to regard the system of physical knowledge as a network system, a physical concept is a node in the network, and its connotation is a high generalization of people's understanding of the essential attributes of related things. Because concept is a sudden change from quantity accumulation to quality in the process of human cognition, it is a sign of the development level of human thinking ability. Therefore, the process of learning and understanding concepts is the process of developing thinking potential and ability by using scientific thinking methods. The most basic criterion for judging, understanding and mastering physical concepts is whether you really understand the connotation and extension of the concepts you have learned.
Physical concepts can be roughly divided into two categories. One is the concept of physical properties, which directly reflects the characteristics of things and substances, such as particles, insulators and electric fields. For them, it is usually expressed in qualitative language to explain what they are. The other is the concept of rationality, which is used to reflect the principle of things (including processes and phenomena) and the essential attributes of things, such as force, energy, electric field intensity, capacitance and so on. There are qualitative and quantitative methods. For qualitative, we only need to explain what is qualitative, such as inertia, interference and so on. For quantification, we should not only explain what it is, but also what it is equal to, such as work and potential.
Middle school students often find physical concepts abstract and difficult to learn, mainly because they don't really understand them. Therefore, when solving problems, we often memorize physical concepts, which leads to mistakes. In view of the above problems, students should make efforts in the following points when understanding physical concepts.
First, the establishment of ideal model can describe physical phenomena vividly, which is beneficial to the establishment and understanding of concepts.
The so-called "ideal model" is an abstract model established after things are air-dried and vine-removed in order to grasp the essence of things and solve problems. The process of any physical phenomenon is mostly complicated, and it is difficult to describe them. However, in some cases, by excluding secondary factors, grasping the main aspects of the problem, abstracting concrete things, replacing the actual research objects with idealized physical models, and simplifying the relevant processes, we can vividly describe physical phenomena and establish concepts for theoretical research. For example, the movement of falling objects is just a messy picture in people's minds at first: heavy rain is pouring and sand is falling ... If we carefully observe related phenomena or do experiments, the picture in our minds will be more concise. Raindrops and sand fall vertically faster and faster in a pattern, and they all become "objects" without personality. In this case, these objects can be regarded as geometric points with only mass but no shape and size. This object model is called "particle". Furthermore, we ignore the blocking effect of air resistance on the falling motion of "object" and agree that its initial velocity is zero, so that the mind can establish a physical model of free falling motion. The physical model is based on experiments or observations, and it is an approximate but prominent description of physical facts. In this way, attaching importance to the establishment and understanding of physical models can provide better means and methods for students to accept knowledge.
(A), in-depth study of teaching materials learning outline
It is clearly pointed out in the syllabus that attention should be paid to guiding students to learn basic concepts and the wide application of basic laws in teaching. Knowledge is the result of human understanding of the phenomena, facts and laws of objective things, and it is the source of enhancing wisdom and strength. Basic knowledge is the basic facts that constitute various disciplines and their corresponding basic concepts, principles and formulas. [1] For physical concepts, students should generally understand their meanings and understand the differences and connections between concepts. The teaching of basic physics knowledge must distinguish between primary and secondary, highlight the key points and grasp the key points. These incisive expositions on physical concepts in the syllabus should be used as a guide to do well the teaching of physical concepts. Effectively mastering the "two basics" means paying special attention to mastering basic knowledge and skills on the basis of accurate understanding. If the learner's understanding of "double basics" is not exact, then mistakes will also occur in the transfer process. If learners just memorize "double basics" by rote, even if they know it by heart, they don't understand it, and it is of little significance to produce positive transfer. To master the "double basics" effectively, we should pay special attention to mastering the knowledge structure. The so-called knowledge structure is the various relationships between basic concepts, concepts and principles, and principles and principles. It is more general and universal than individual and isolated knowledge and skills, so it is easier to realize the positive transfer of learning. [ 1]
According to the requirements of the syllabus, this paper analyzes the purposefulness and scientificity of the concepts appearing in the textbook. It must be clear: why is this concept put forward in physics? How is the concept expressed scientifically? What is its position and function in physics? Specifically, we should seriously study the following aspects: First, clarify the physical facts (including experimental facts) related to physical concepts, that is, clarify the basis of physical concepts. Second, it is necessary to clarify what problems these physical facts raise that need further study, that is, to clarify the necessity of introducing concepts. Third, what means and methods are used in the study. Fourth, we should scrutinize the meaning of the concept word for word and fully and accurately understand its physical meaning, especially the applicable conditions of the concept. We should also master the definition and units of physical quantities. Fifth, it is important, difficult or key to clarify the differences and connections between closely related concepts and their positions in textbooks.
Through the study of teaching materials, it is necessary to clarify the position of a certain physical concept in the whole teaching materials, so as to distinguish between primary and secondary, highlight key points, grasp key points and handle key points well. In this way, the teaching of physical concepts has a solid foundation.
(B), vivid and intuitive introduction of concepts
Concept introduction is an important link in concept teaching. If the lead-in work is done well, it can stimulate students' enthusiasm for learning concepts from the beginning, put their thinking on the right track, and have a direct impact on correctly understanding and mastering the essentials. Physical concept is the essential abstraction of physical phenomena, which is formed by analyzing, synthesizing, abstracting, summarizing and other thinking activities on the basis of perceiving a large number of materials. Concepts should also be introduced from intuition to abstraction according to this feature. For example, when talking about the concept of strength, we should first give some familiar examples in students' daily life. Such as: ① portable bucket; ② Carriage; 3 kick the ball with your feet; ④ Magnets attract iron, etc. Then these examples are analyzed, compared, summarized and concluded. The definition of force is "force is the action of objects on objects". Let the students understand that force is the interaction between two objects. Such as hands and buckets; Horses and carriages; Feet and football; Magnets and iron blocks. It should be more clear that there is not necessarily a strong existence between two isolated objects, and there must be an interaction between the two objects.
Second, pay attention to creating situations and understanding concepts through experience.
Einstein said, "Interest is the best teacher". Teachers should be conscientious people in life, carefully design, so that students can experience physics in life and experience the fun of physics. For students who like to study alone and are unsociable, teachers should encourage them to actively participate in group learning activities and conduct more cooperation, communication and expression training with others. [2] If this is done, the student will really be interested in physics, and he will learn and understand spontaneously. For example, when helping students understand the concepts of overweight and weightlessness, prepare scales in advance. In class, first ask: Did the pointer on the scale change when people stood on the scale and squatted down? If so, what was the result? On the contrary, what will be the result? Let the students guess first, then practice in person, and draw the concepts of overweight and weightlessness from the facts. Among the basic elements of curriculum and teaching, teachers (or teachers' activities) and students (or students' activities) are the most basic and essential. Teaching activities are organized for students. Without students, teaching activities are unnecessary and possible. Teaching activities guided by teachers can only be called "teaching activities" in the true sense, otherwise it can only be regarded as "self-study". In the teaching system, teachers rely on the conditions and resources provided by the environment, take teaching materials as cultural media, have the widest social interaction with students, promote the healthy growth of students, and realize their own development. [3] Therefore, teachers should strive to create scenarios, so that students can actively explore and experience, and learn knowledge and understand concepts through their own activities as much as possible.
(A), revealing the nature of the concept, understanding the concept
Physics teaching practice shows that only by understanding concepts can students grasp them firmly. To make students understand the concept, they must master the essence of the concept. Intuitive materials are the basis of forming concepts, but concepts cannot be directly derived from intuitive materials. Only through students' thinking can perceptual knowledge be sublimated into rational knowledge, which is a leap in understanding and a key step for students to form concepts. In order to achieve this leap, we must start students' thinking. In concept teaching, there are many common thinking methods, such as comparison, analysis, synthesis, abstraction, generalization, judgment and induction. Only by guiding students to think correctly can we reveal the essence of concepts and enable students to master concepts comprehensively.
(2) Grasping differences, looking for connections and deepening concepts.
In order to make students understand the essence of concepts more deeply, we must pay attention to the differences and connections between the main points. Some similar related concepts seek similarities and differences, and the concepts are deepened repeatedly.
For example, "speed" and "acceleration" are two important concepts in mechanics, which need students to understand deeply. In teaching, we should make a comprehensive comparison between these two concepts and find out the differences and connections. Let the students know that speed is a physical quantity that describes the moving speed of an object, or the speed at which the position of an object changes. The greater the speed, the faster the object moves or the faster the position changes. Acceleration is a physical quantity that describes the change of speed. The greater the acceleration, the faster the speed changes. Speed is equal to the ratio of displacement to time, and acceleration is equal to the ratio of speed change to time. The speed depends on the displacement and the time required for the change, and the speed is not necessarily large when the displacement is large. Acceleration depends on the change of speed and the time required for the change, but not on the size and change of speed. Velocity and acceleration are both vectors. In linear motion, the direction of velocity is the direction of displacement, and the direction of acceleration may be the same as or opposite to that of velocity. When the speed increases, the acceleration direction is the same as the speed direction; When the speed decreases, the acceleration direction is opposite to the speed direction. Through the above comparison, students can have a deeper understanding of the two concepts of "speed" and "acceleration".
Third, choose your words carefully, from the outside to the inside.
In the process of studying physics, we often find that the literal contents of many physical concepts can show their basic physical meanings. For example, the periodic changes of electromagnetic oscillation, electric-electric field, magnetic-magnetic field and oscillation-oscillation are the repeated alternating changes of electric field and magnetic field, which is the physical connotation of electromagnetic oscillation. For another example, electricity-current, resistance-obstruction, strung together is the obstruction of current. But remind everyone that some concepts are synonyms of different words. For example, the meaning of the word "electricity" in the above two concepts is different. In the process of biting "Wen", we are often confused by some appearances, such as "uniform circular motion" Beginners see the word "uniform speed" and think its speed is constant. In fact, "uniform speed" here does not mean uniform speed, but uniform speed, but its direction is changing, so the vector of speed is also changing. Therefore, when learning this kind of concept, we should understand the concept as a whole and learn from it.