We must pay enough attention to a large number of scientific methods contained in physics teaching, and infiltrate them into teaching activities, introduce and guide students in time, let students experience and appreciate these scientific methods in learning activities, gradually improve their scientific inquiry ability, master some scientific methods, and lay a good foundation for students' lifelong learning. In junior high school physics curriculum standards, scientific inquiry is not only the learning goal of students, but also one of the important teaching methods. In the process of exploring scientific laws, students can experience the fun of scientific inquiry, learn scientists' scientific inquiry methods, understand scientific thoughts and spirits, master scientific learning strategies and scientific thinking methods through hands-on and brains, and through the process of "rediscovery" known in physics, thus improving scientific quality. In order to make physics teaching reach the goal set by the new curriculum standard, we must attach importance to a large number of scientific methods contained in physics teaching, infiltrate them into teaching activities, introduce and guide students in time, let students experience and appreciate scientific methods in learning activities, gradually improve their scientific inquiry ability, master some scientific methods, and lay a good foundation for students' lifelong learning. Let's discuss some common scientific methods in physics teaching. First of all, guessing ideas plays an important role in the learning process of scientific inquiry. It is the most active component of physical wisdom, and it is also an important link to cultivate students' guessing ability in the process of physical inquiry, and guessing determines the direction of scientific inquiry. Therefore, in the process of physics teaching, it is particularly important to guide students to guess scientifically and reasonably. First of all, guessing should be based on certain experience and knowledge. In the teaching of scientific guessing ability, students can be allowed to spread their imagination wings to solve problems, encourage them to speak out all possible situations boldly, and then analyze them one by one according to their existing knowledge and life experience, think about what facts are supported in life and whether they are consistent with existing knowledge, exclude those ideas that contradict experience and knowledge, and leave scientific guessing. Without certain knowledge and experience, speculation can only be a tree without roots and water without sources. Therefore, in order to avoid students' random guessing in teaching, it is an effective means to avoid classroom chaos and one of the methods to cultivate students' inquiry ability. In addition, teachers should pay attention to the direction when guiding students to guess. In the process of students' independent inquiry, teachers' guidance can make the finishing point. Due to the limitation of classroom teaching time and equipment and students' knowledge, it is impossible for us to explore what students say one by one. Only by selecting the essence from the rough, discarding the false and retaining the true, can the inquiry process be successfully completed. For example, when guessing what factors kinetic energy is related to, students may guess factors such as mass, speed, gravity, slope and height. Special attention should be paid to let students tell the reasons and basis for guessing, and can cite relevant examples to prove it. Then the teacher guides the students to classify similar factors into one category, that is, mass and gravity can be classified as quality, and slope, height and speed can be classified as speed. In this way, kinetic energy is summarized as related to two factors: mass and speed. At the same time, guiding students to review the experiment of Newton's first law, we can know that if we want to control the same speed of an object reaching an inclined plane, we must control the same height of the object sliding down the inclined plane. Then through the research method of controlling variables, this inquiry experiment is not difficult to complete. After completing the experiment, the teacher can do another experiment, that is, double the mass and speed respectively, and observe the distance that the box is pushed, so as to judge which of the two factors has greater influence on kinetic energy, thus laying the foundation for further study in senior high school. Of course, it is impossible to cultivate students' guessing ability overnight. We need our teachers to pay attention to the cultivation of this ability in the teaching process and always pay attention to guiding students to make reasonable guesses in order to achieve the purpose of quality education. Second, the control variable method "control variable method" is a scientific method commonly used in junior high school physics inquiry. In many cases, the factors affecting the physical research object are not single, but many factors are intertwined and work together. Therefore, in order to accurately grasp the characteristics of the research object and understand the causes and laws of things, we must artificially create some conditions to facilitate the study of problems. For example, when a physical quantity is related to several factors, we usually study the relationship between the physical quantity and each factor separately, and then draw a conclusion through comprehensive analysis. In this way, when studying the relationship between physical quantity and one of the factors, we must artificially control other factors to keep them unchanged, so as to observe and study the relationship between physical quantity and this factor. This is the method of "controlling variables". There are many concepts or laws in junior high school physics teaching, so we should control variables. For example, when I first came into contact with physics in the eighth grade, there was an inquiry experiment to explore "how does sound spread from a sounding object to a distance?" . Let one student tap on the desktop at one end of the table, and the other student listens to the sound at the other end, once against the desktop and once just near it. It is found that the sound can be heard twice, and the students are guided to analyze that the two kinds of sounds spread through the table and the air respectively, indicating that the sound depends on the medium. At the same time, let the students compare the sounds heard twice, so as to realize that the sound travels faster in solid than in air, that is, the solid has strong sound transmission ability. Here, the teacher must emphasize that the variable that needs to be controlled in the experiment is that the distance of listening to the sound is the same as the intensity of hitting the desktop, so that students can experience the idea of controlling the variable and prepare for the future inquiry experiment. The experiments in which the control variable method is also used in junior middle school physics include: What are the factors that affect the tone and loudness of sound? What factors are related to evaporation rate? What factors are related to the resistance of a conductor? The relationship between the current in the conductor and the voltage at both ends of the conductor and the resistance of the conductor, and what factors are related to the size of electric heating? What are the factors that affect the magnetic induction intensity of electromagnets? What factors are related to the direction of induced current? What factors are related to the force direction of charged conductor in magnetic field? What factors are related to the action of force? What are the factors that affect sliding friction? What are the factors that affect the stress effect? What factors are related to the pressure of liquid? What factors are related to the study of buoyancy? What factors are related to kinetic energy or potential energy? Study what factors are related to how much heat an object absorbs and so on. Control variable method is the most commonly used and effective scientific method to explore objective physical laws. Through the control variable method, we can easily study the qualitative or quantitative relationship between a physical quantity and multiple factors, and thus get the universal law. Third, the method of equivalent substitution has a well-known historical story-the image of Cao Chong. He used the concept of equivalent substitution. He replaced the elephant with a stone and skillfully measured the gravity of the elephant. Of course, the idea of "breaking the whole into parts" is also used here. Many great men often use equivalent methods to simplify research problems. For example, Edison made a round shadowless lamp equivalent to many suns with the light reflected by a flat mirror. When his assistant Aptom was trying to calculate the volume of the light bulb, Edison told him that he only needed to fill the light bulb with water, and measuring the volume of water was the volume of the light bulb. In addition, Archimedes found a method to identify the true and false crown in the bath, which also led to the discovery of an important principle-Archimedes principle. In this way, when the measuring equipment can't directly measure a physical quantity, we should try to replace the physical quantity that can't be directly measured with the physical quantity that can be directly measured. This is the "equivalent substitution method". When using this method, the only thing that needs attention is that there is an internal relationship between physical quantities that cannot be measured directly. Find this inner connection, and complete the design of the experiment. It can be said that the idea of "equivalent substitution" is the most fundamental and important idea for the success of physical experiments, and the relevant laws, theorems, formulas and principles in physics are all based on substitution thinking. For example, measuring the volume of irregular solids is to use the principle that when an object is immersed in liquid, the volume of the object is equal to the volume of the liquid discharged by the object, and the V-shaped object is replaced by a V-row. When there is a measuring cylinder or cup, the "drainage compensation method" or "equal space occupation method" can be used for measurement. In the absence of measuring cylinder and measuring cup, we can use spring balance and water to calculate V row (total immersion) by measuring buoyancy combined with Archimedes principle, or use balance to measure drainage quality (total immersion), and then use density knowledge to calculate V row. If the mass of an object cannot be measured directly, we can use the principle of F-float = G to float, and then we can know g by measuring F-float, and then we can get the mass of the object. This alternative measurement method of mass or volume is usually more common in the method of measuring the density of substances. Many physical quantities are measured by equivalent substitution method. Equivalent substitution method can also be used for the equivalence of some equipment. If it is impossible or difficult to reveal the physical essence directly due to the special limitation of the experiment itself or experimental equipment, it can be replaced by equivalent phenomena with similar or * * * characteristics, so that not only can the conclusion be drawn smoothly, but also it can be easily accepted and understood by students. For example, in the experiment of exploring the imaging law of flat mirror, the glass plate is used instead of the flat mirror, which is easy to be accepted by students because of their similar imaging characteristics, and the glass plate is transparent, through which the candle behind the glass plate can be observed, which is convenient for studying the characteristics of the image and revealing the imaging law of the flat mirror. With the inspiration of these scientific methods, students may be able to use them freely when they encounter related problems in the future. For example, after learning to measure resistance by voltammetry, students are required to design an experiment. What should I do if I need to measure the resistance of an unknown resistor without a voltmeter or ammeter, but give another constant resistance? Students can use the idea of equivalent substitution to design, that is, to make the ammeter equivalent to a voltmeter in series with a fixed resistance, or to make the voltmeter equivalent to an ammeter in parallel with a fixed resistance. Whenever students solve a problem by themselves, they will definitely have a feeling of "bright future", and their interest in physics will naturally increase a lot. Fourth, the conversion method The so-called "conversion method" mainly refers to the conversion of invisible and difficult-to-see phenomena into visible and easy-to-see phenomena under the premise of ensuring the same effect; Turn unfamiliar complex problems into familiar simple problems; A method of converting physical quantities that are difficult to measure or measure into physical quantities that can be measured or measured. For example, in the experiment of studying the relationship between electric heating power and resistance, the heat generated by current passing through two resistance wires with different resistance values cannot be directly observed and compared, but we can observe the temperature change of kerosene by converting it into the heat absorption of kerosene, thus deducing that the resistance emits more heat. Then, can we use other methods instead of kerosene to observe the heating of the resistor after it is electrified? This can disperse students' thinking, train students' transformed thinking methods and improve students' ability to design experiments. The principle of spring dynamometer also means the principle of indirect measurement. That is, directly measurable quantities are used to indirectly represent those quantities that are inconvenient for direct observation and measurement. Here, the change of spring length can be directly observed and measured, but the force is invisible and unpredictable, but the force is related to the change of spring length, so we can measure the force by the elongation of the spring. Not only dynamometer, but also thermometer, pressure gauge, barometer (altimeter), ammeter, voltmeter and clock speedometer. What we see is the change of length and angle, which reflects the change of temperature, liquid pressure, atmospheric pressure (height), current, voltage, time and speed. The principle of transformation method is used in many places in junior middle school physics. When studying what factors are related to the heat absorption of an object, we can judge the heat absorption by observing the heating time of the same electric heater put in it. Diffusion phenomenon is used to study the movement of molecules and the speed of molecular movement. When studying the size of kinetic energy or potential energy, we can infer the size of kinetic energy and potential energy by observing the distance that the moving ball pushes the carton or the depth that the stake hits the ground. When studying force, current and magnetic field, because they are all invisible and intangible things, we can use the function of force, various effects of current and the basic properties of magnetic field to study. For example, we can know the function of pressure by the depression degree of foam, sense the current by the brightness of light, and judge its magnetic strength by the number of needles attracted by electromagnet. Observe the propagation direction of light by transforming the propagation of light in transparent air into the propagation in smoke or water mist. For another example, the transformation method is used to amplify the tiny vibration of the sounder through the vibration of the foam plastic ball, to amplify the tiny change of the object's thermal expansion and cold contraction through the height change of the liquid column in the thin tube, and to amplify the tiny deformation of the object after being stressed through the deflection angle of the light reflected by the plane mirror. The transformation method can transform the research object, space angle, physical law, physical model, thinking angle, physical process, physical state and time angle, which can simplify the complex and solve the problem indirectly. This is of great benefit to cultivate students' imaginative design ability and creative thinking quality. V. Idealized Methods Throughout the history of physics development, many important discoveries and conclusions are due to the scientific and idealized physical model created by scientists through bold guesses and verified by experiments or practices, and obtained under the foreshore where the model is in good agreement with the factual basis. Galileo and Newton established an idealized smooth model, which made them make a great discovery of the law of inertia. 1852, Faraday conceived the model of electric field lines and magnetic lines for the substances existing in the space around the charged body and magnet, and showed the distribution shape of magnetic lines around the magnet with iron powder, thus establishing the concept of field, which is a major breakthrough in the current traditional concept. Rutherford also conceived the nuclear structure model of atoms in 19 1 1. The research method of replacing objective prototype with idealized model is "idealized method". It is divided into "ideal experimental method" and "ideal model method". For example, when we study whether vacuum can transmit sound, we can clearly hear the bell by putting a small bell in a closed glass cover and connecting the circuit. We use an air pump to gradually pump away the air in the glass cover, and the bell becomes weaker and weaker, indicating that the thinner the air, the weaker the sound transmission ability of the air. Absolute vacuum can't be achieved in the experiment, but it can be inferred from Bell's changing trend that vacuum can't transmit sound, which is very similar to the establishment process of Newton's first law. This is an ideal experimental method. If teachers pay attention to this method in teaching, it will help to cultivate students' scientific thinking and improve their innovative ability. In junior high school textbooks, we are familiar with idealized models: lever (anything that can rotate around a fixed point can be regarded as a lever), inclined plane (a curved surface with a low starting point and a high ending point like Panshan Highway can be regarded as an inclined plane), axle (a machine in which a part rotates to form a circular trajectory, such as a door handle, a car steering wheel, a pedal and a wrench, can be regarded as an axle), and connector (a container with an open top and a connected bottom). It is the introduction of these idealized physical models that enable us to face many complex practical problems and solve them smoothly through simplified processing. We often use idealized methods to solve some problems by finding and establishing suitable idealized models, that is, idealizing the research objects and conditions, so as to achieve the purpose of simplifying the complex. In addition, the commonly used scientific methods include analogy, image, induction, comparison, deduction, reasoning, imagination, reverse thinking, macro-micro combination, accumulation, differentiation and so on, which will not be described here.