Physical model in middle school physics.
This paper expounds the concept and function of physical model, six common physical models in middle school physics textbooks, the position and function of physical model in middle school physics teaching, and some problems that should be paid attention to in the teaching process of physical model in middle school.
Keywords: middle school physics; Teaching; physical model
First, the concept and function of physical model
The practical problems of physical analysis and research are often very complicated and there are many influencing factors. In order to facilitate analysis and research, physics often adopts a? Simplify? In this paper, the practical problems are scientifically abstracted, the main factors are retained, and the secondary factors are omitted, and an ideal material (process) or imaginary structure that can reflect the essential characteristics of the original object is obtained. This ideal material (process) or imaginary structure is called a physical model.
Physical models can be divided into idealized physical models and exploratory physical models according to their design ideas. The former is characterized by highlighting the main contradiction of the research object, ignoring the secondary factors, and abstracting the object into a substance (process) that only has the main factors of the original object and objectively does not exist, thus simplifying the problem. Such as particle model, point charge model, ideal gas model, uniform linear motion model and so on. The latter is characterized by imagining the existing form of matter according to the results of observation or experiment, but its essential attributes are still being further explored. Such as atomic model, wave-particle duality model of light and so on.
The main functions of establishing and studying physical models are:
First, it can greatly simplify the handling of problems without big deviation, from which the basic laws of object motion can be easily obtained;
Second, the results of model discussion can be slightly modified for the analysis and research of practical things;
Third, it is helpful to truly understand the objective physical world and achieve the purpose of understanding the world, transforming the world and serving mankind.
Second, several physical models often encountered in middle school physics textbooks
Physical models can be divided into:
1. Physical object model is to model the research object of physical problems.
For example, a particle should give up or ignore its shape, size, rotation and other properties, highlight its position and mass characteristics, and describe it with a point with mass, such as point charge, spring oscillator, simple pendulum, ideal transformer, ideal electric meter and so on. All belong to the idealization of the object itself.
In addition, such as point light source, electric field line, magnetic induction line, etc. It belongs to the concept that people use idealized graphics to simulate according to physical properties.
2. The physical process model is approximate to the actual motion process of the research object. Eliminate the interference of some minor factors in the actual movement process and make it an ideal typical process.
For example, study the process of an iron ball falling from a static position in the sky. First of all, consider the attraction, expressed by the formula F=GMm? R2 shows that the closer the iron ball is to the ground, the greater F, and then the influence of air resistance, wind speed and earth rotation should be considered. In this way, the process of testing the whereabouts of iron balls is very complicated and inconvenient to study. Therefore, in the process of research, we highlight the main factor of iron ball falling, that is, it is influenced by gravity, while ignoring other secondary influences, and regard gravity as a constant force. Through this simplification, the research problems are simplified, and the research results will not affect the correctness of the basic laws. Thus, it becomes a typical movement process in physics, that is, free fall. This physical model is called the process model.
Uniform linear motion, simple harmonic vibration and elastic collision in teaching materials; The isothermal, isovolumetric, isobaric and adiabatic changes of ideal gas all simulate the physical process.
3. Is the physical condition model such as the law of free fall established? Ignore air resistance and think that gravity is constant? After the conditional model. Smooth slopes in mechanics; Insulated container; Uniform electric field, uniform magnetic field, etc. In electricity, we should also idealize the environment in which the object is located.
4. Physical equivalent model is to equate phenomena with similar properties or characteristics, substances with similar motion forms and motion by fully excavating the characteristics of the original physical model. For example, the ideal gas molecule is equivalent to an elastic ball, and the gas pressure formula is explained and deduced by the collision between the elastic ball and the wall. The electromagnetic oscillation process is equivalent to a simple pendulum vibration model.
5. The physical experiment model is based on the experiment, grasping the main contradiction and ignoring the secondary contradiction, and then making further analysis and reasoning on the process according to the law of logical reasoning, finding out its law and drawing experimental conclusions.
For example, Galileo put forward his ideal experiment on the basis of experiments: the ball rolling from one chute rolls to another chute, and the smaller the slope of the latter, the farther the ball rolls ―― without friction, the ball rolling from the chute will always move at a constant speed on an infinite horizontal plane, thus overturning the experiment that lasted for more than two thousand years? Force is indispensable for maintaining the motion of an object? This conclusion laid the foundation for the emergence of the law of inertia (Newton's first law).
For another example, when studying the intensity of electric field, imagine putting a point charge in the electric field that will not cause the change of electric field, and investigate its F? Q value and so on.
6. Physical mathematical model is to establish a mathematical model with the physical model as the description object, and quantitatively calculate the objective entity approximation, thus making the problem from complex to simple. For example, the angle between the cycloid of a simple pendulum and the vertical direction cannot be greater than 50, so that the arc calculation can be converted into trigonometric calculation, and so on.
Third, the position and role of physical model in middle school physics teaching
1. Establishing a correct and clear physical model is one of the important methods and powerful means in physics research.
In fact, all kinds of problems studied in physics involve many factors, and the model is established on the basis of grasping the main factors and ignoring the secondary factors. Its image is concrete and vividly reflects the essence and mainstream of things.
Like what? Particles? Model, in the macroscopic translation movement of an object, describes the physical quantities of movement, such as displacement, velocity and acceleration, which are the same for the same object. In the study of these problems, the size and shape of the moving object can be ignored, so the moving object can be granulated, that is, the particle model can replace the real moving object.
2. A correct and distinct physical model itself is one of the important physical contents, which depends on the corresponding physical concepts, phenomena and laws.
The leap from Thomson model to Rutherford model is a vivid reflection in the process of understanding atomic structure.
The establishment of Einstein's photoelectric effect equation successfully explains the photoelectric effect, which is based on reflecting the particle nature of light. Photon? Above the model.
Many facts show that physical phenomena, processes and laws are directly related to their corresponding physical models; A certain physical model is the most vivid and concentrated reflection of the corresponding physical concepts, phenomena, processes and laws, and it is inseparable.
3. The establishment of a correct and distinct physical model makes many abstract physical problems intuitive, concrete and vivid.
For example, electric field lines describe electric fields, and magnetic induction lines describe magnetic fields. Understand the basic viewpoint of molecular model of molecular dynamics theory and the nuclear structure explanation of an experimental phenomenon of particle scattering; The photon model's understanding of the particle nature of light and so on, anyone who studies physics will feel the indisputable important role given by the physical model.
Fourthly, the teaching of physical model should focus on students mastering the basic methods of establishing correct and distinctive physical model.
Physical model is a part of the basic knowledge of physics and belongs to the category of physical concepts. Various physical models created for us before learning are an important part of completing the teaching content. Cultivating students to master this method can clearly reflect a specific physical content, phenomenon or process. Physical map? , is an important aspect of cultivating students' scientific thinking ability. To this end, we should pay attention to the following points in teaching:
1. Explain the basis of each physical model design. The physical model looks independent, but the idea of designing the physical model is the same.
2. Teaching physics models should echo each other. Kinematically established? Particles? It can be developed into the model of particle dynamics, the law of universal gravitation and even the problem of object rotation, and can also be extended to the oscillator of pendulum ball and spring oscillator in simple pendulum, and even help us to establish the point charge model in electricity and the point light source model in optics.
3. Physical model thinking runs through the process of physics teaching. With the deepening and improvement of people's understanding of a physical problem, the physical model will be improved and accurate. For example, regarding the nature of light, people talked about wave-particle duality from Newton's particle theory, Huygens' wave theory, electromagnetism theory and particle theory, and the model of light deepened again and again in this development process.
4. In the usual example teaching, the important position and function of physical model are also reflected everywhere. To solve all kinds of physics exercises, it is an important link for students to establish corresponding physical models according to the meaning of the questions. If the physical model understood by the problem solver is consistent with the design model of the proposer, the meaning of the problem will inevitably become clear and the difficulty of the exercise will be broken. This kind of example is easy to find.
In a word, we really need to pay enough attention to the teaching of physics model, which has a great relationship with improving our physics teaching level.
Physics conjecture and physics teaching in middle schools.
This paper expounds the significance of physical conjecture in middle school physics teaching and the methods for teachers to guide students to make physical conjecture in physics classroom teaching.
Keywords middle school physics conjecture physics teaching
China Library Classification G Document Identification Code A
The article number is 0450-9889 (2014)11b-0076-02.
With the gradual deepening of basic education curriculum reform, in the new curriculum standards, higher requirements are put forward for high school students' learning ability in the process of learning physics, so teaching students to use the method of physical conjecture can make them learn physics more effectively. In order to promote middle school students to learn to use the method of physical conjecture, the physics textbook of the new curriculum has specially designed many activities to study physical phenomena. This can improve students' understanding of physics knowledge and their ability to learn physics knowledge, such as asking questions, guessing assumptions, cooperating and communicating, etc. These basic abilities are the premise and foundation to ensure the smooth scientific research of various physical phenomena. Only through speculation, hypothesis and many research activities can we successfully complete the process of studying physical phenomena. Based on the author's teaching experience for more than ten years, this paper summarizes the role of physical conjecture in senior high school physics teaching and how to improve the experience of physics teaching through physical conjecture. Now I will talk about my own views.
1. Physical conjecture is of great significance to physics teaching in middle schools.
In the physics course of compulsory education in the new curriculum standard, it is proposed that students should be encouraged to actively and boldly carry out scientific research, so that students can learn scientific research methods from the basic scientific research process, and finally achieve the goal of improving scientific research ability. Make students form the scientific habit of respecting facts and boldly imagining, and carry forward the scientific spirit of studying truth; Cultivate students' confidence and determination to dare to question, innovate and overcome difficulties. The role of teachers in middle school physics teaching is to guide students to make scientific guesses, guide students to carry out scientific exploration activities, and enhance students' scientific exploration and innovation ability. Encourage them to make guesses and assumptions according to the physical knowledge and phenomena they have learned, and then design experiments to verify their guesses and assumptions by doing their own experiments. Therefore, in order to meet the requirements of the new curriculum standard, the author thinks that the application of conjecture in the teaching process of the new curriculum standard plays a key role. The application of physical conjecture is the requirement of the development of education and teaching, and it is also the need to promote the reform and development of physics education and teaching. The author believes that it is of great significance to apply the idea of physical conjecture in middle school physics teaching.
1. Improve students' interest in learning and enhance their initiative in learning.
Students are often curious about new things, and they all want to know the knowledge, laws and mysteries as soon as possible. If students are encouraged to guess some possible phenomena or laws about the physical phenomena to be studied in the middle school physics teaching process, it will not only enhance students' sense of novelty, but also stimulate students' inquiry consciousness and ability, so that they can actively learn new knowledge. Training and cultivating middle school students' physical guessing ability can improve students' interest and desire to study physical problems. Interest and desire are the motivation for students to learn physics knowledge. Therefore, physical conjecture is a good way to improve students' interest in learning and promote students' active learning.
2. Improve students' thinking ability
In the process of physics teaching in middle schools, teachers should always ask questions according to students' existing knowledge and ability to understand problems, guide students to guess, and conduct strict reasoning and verification through observation, experiment, induction and summary, so that students can gradually improve their divergent thinking ability and make their thinking more flexible in the process of learning physics knowledge. Therefore, guessing ideas is not only convenient for students to understand and master physical knowledge, but also helpful to improve their thinking ability.
This is helpful for students to consolidate their knowledge of physics.
Physical conjecture is an open way of thinking for students to speculate according to their own thinking consciousness. After careful observation and identification of things, students' research on the integrity of things is improved, students' thinking process is promoted, and students can quickly understand and master new knowledge. If this new knowledge comes from students' own active guesses and verified reasoning, students will be more receptive. Therefore, these physical phenomena and laws will be deeply engraved in the hearts of students, consolidating these new physical knowledge.
4. Cultivate students' innovative ability
In the new curriculum standards, the cultivation of middle school students' innovative ability is particularly emphasized. Scientific physics conjecture is one of the main methods to cultivate middle school students' innovative ability. Scientific physical conjecture plays a positive role in cultivating middle school students' innovative ability, and can improve students' reaction ability and flexible problem-solving ability. Therefore, scientific physical conjecture can effectively improve the innovative ability of middle school students.
Second, teachers guide students to make physical guesses in physics classroom teaching.
In order to exert students' imagination as much as possible in the teaching process, teachers should guide students to guess according to their own physical knowledge, hobbies and imagination. How can teachers better guide students to use the physical knowledge and skills they have mastered to construct new physical conjectures? The author believes that teachers need to pay attention to some guessing methods in the actual teaching process.
1. Inspire students to guess according to their own experience, experience and knowledge.
The experience of scientific development tells us that scientific speculation is not random speculation, but needs scientific basis, based on students' experience, experience and common sense of life. Einstein founded it? Relativity? At first, it was based on predecessors' experience, my own experience and my own scientific knowledge. Then through observation, reasoning, deduction and proof, the theoretical basis is put forward, and finally the world-famous? Relativity? . Like studying? Free fall? First, let the students observe the feathers and iron pieces falling at the same time in a glass tube with air, and then inspire them to guess what will happen if the air in the glass tube is pumped out and the feathers and iron pieces fall at the same time. Let the students guess and write down these guesses, then let the students observe through demonstration experiments, and finally draw a conclusion. This teaching method, which combines inspiring students to guess and demonstrating experiments, can deepen students' understanding of the physics knowledge they have learned.
2. Encourage students to discuss and summarize physical conjectures.
In the process of teaching, students should be divided into several groups, each group should put forward its own different guesses, and each group should state the reasons and basis of its own guesses. Encourage them to discuss and demonstrate, and improve their interest and enthusiasm for physical conjecture through discussion and demonstration. Like studying? Newton's second law? Students are divided into two groups. One group guesses the relationship between acceleration and force, and the other group guesses the relationship between acceleration and mass. Then let them do experiments and come to a conclusion. After listening carefully to students' opinions in class, the teacher induced them to discuss and guess the relationship between acceleration and force and mass, and finally summed up Newton's second law. In this way, the teaching task can be better completed and better teaching effect can be achieved.
3. Encourage students to make bold guesses.
In the process of teaching, many students are ashamed to speak, because they are afraid that their guesses will be teased by other students or accused by teachers of being incorrect. At this time, teachers should encourage and guide students to make bold guesses and eliminate their concerns. For example, when studying the refractive index of glass, we can guess whether the propagation direction of monochromatic light changes after passing through parallel glass bricks. First, encourage students to boldly guess their exit direction and write it down. Regardless of whether their guesses are reasonable and accurate, teachers should keep a balance and let experiments verify the results. Only in this way can we improve students' learning enthusiasm and enhance their awareness of scientific conjecture.
4. Create a good guessing condition
In the teaching process, teachers should actively guide and encourage students to guess when teaching content that is conducive to cultivating students' guessing ability. For example, in? Lenz's law? In teaching, before demonstrating the experiment of making the N pole of the magnet close to the closed aluminum ring in class, the teacher first inspires students to guess what will happen if the N pole of the magnet is close to the closed aluminum ring and what will happen if the N pole of the magnet is close to the notched aluminum ring. Then guide students to observe the experimental phenomena through experiments. Similarly, what happens when the S pole of the magnet is close to the closed aluminum ring? In short, teachers should try their best to create conditions for students to guess.
Physical conjecture is both a free attempt and a rigorous creation. Therefore, in the teaching process, teachers should be good at grasping all opportunities that are conducive to improving students' guessing ability, encouraging students to guess boldly, thus improving their thinking ability and increasing their interest in learning physics, thus improving the efficiency of physics teaching.
refer to
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