The sharing of physics answering skills in college entrance examination 1. Multiple choice problem
There are ***7 multiple-choice questions in college entrance examination physics. The time for multiple-choice questions in physics should be 17 ~ 22 minutes. In seven multiple-choice questions, time cannot be evenly distributed. Under normal circumstances, the difficulty of multiple-choice questions will gradually increase, and the difficult questions will take about 3 minutes or even longer, while the less difficult multiple-choice questions will generally be solved within 1 minute. According to the relationship of 2: 5: 1, there are generally two simple questions, three intermediate questions and two difficult questions (questions 5 and 7).
Generally speaking, two of the first five multiple-choice questions are related to calculation, and the other three questions are all about understanding basic knowledge and basic laws and using these knowledge to make some qualitative reasoning. The last two multiple-choice questions usually involve calculation or even drawing, which is really uncertain and can be ruled out. Usually, it is easier to judge whether there is a correct answer. Students with average grades can only choose one, 3 points. )
You must pay attention to some key words when solving problems, such as? Incorrect possibility? With what? Are you sure? To discuss the difference between the two, we should discuss various possibilities (especially vibration and wave, the movement of charged particles in the magnetic field). Don't skip the questions, do them in the order of the questions, and start slowly, so that the nervousness you just played will gradually calm down, the thinking of doing the questions will gradually become active, and you will be able to enter the state wholeheartedly before you know it. Generally speaking, familiar questions, questions and pictures are familiar, so we should give new solutions; When you encounter strange problems, strange pictures and strange physical scenes, you should solve new problems regularly. If you still have no idea after analyzing for a long time, skip it for a while, do the following questions first, and then solve them slowly when all the questions you can do are finished (at this time, the mood of solving problems will be relatively relaxed and the state will be easier to play). When you really can't do it, don't give up the chance to guess the answer. First, use the elimination method to eliminate the identifiable interference items. If you can rule out two items, then one of the other two items must be the correct answer, and then choose one at will. Don't give up even if you can't rule out a distractor. Choose one of the four options. It is particularly important to note that you must draw a card immediately after the multiple-choice questions are completed.
Although the multiple-choice question of physics in college entrance examination is the most difficult of all subjects, if the method is chosen well, there will be rules to follow when solving problems. In order to handle multiple-choice questions in college entrance examination with ease, we should first understand the general characteristics of multiple-choice questions, classify multiple-choice questions in college entrance examination, and then study countermeasures according to their respective types.
The first category: the relatively independent part of knowledge points.
The most typical examples are vibration and fluctuation, optics, transformer and long-distance power transmission, and celestial motion knowledge. The knowledge points are relatively independent, and there are corresponding answers to such problems, such as gravity providing centripetal force when celestial bodies move in a circle, and the relationship between the turns ratio of primary and secondary windings of transformers and the voltage ratio, which are easy to form certain regular topics. It is not difficult to master the methods of solving this kind of problems, but these problems are generally small and require a large amount of calculation, so it is necessary to draw a conclusion through simple calculation, which requires students to have the corresponding calculation ability while mastering the methods, and the calculation between various formulas is often complicated.
For this kind of problem, we don't need to solve it with the conventional solution of calculation problem, but only need to solve the final result, so we don't need methods, steps and logical reasoning. How to do it is relatively simple. Many methods that are difficult to express when doing calculation problems can be used, such as extreme value method, special value method and mirror image method, and it is not necessary to do the problems in order. Which option is easy to draw a conclusion, you do it first.
The second category: image category
In recent years, the image problem is a kind of topic with very high frequency in the college entrance examination. This kind of topic is difficult and comprehensive, especially the ability to combine students' image with practical problems. Common images are v-t images, x-t images, F-x images, P-t images, e-t images, i-t images, u-I images, B-t images and so on.
The essence of image problem is to find the physical meaning of abscissa and ordinate first, and then find the functional relationship between the corresponding physical quantities according to the requirements of the topic, paying special attention to the meaning expressed by intercept, slope, area and bending direction. For an image whose physical quantity changes with time, we should study it in sections.
The third category: comprehensive category
Comprehensive problem is a kind of problem that combines several extremely important knowledge points in high school physics and presents it through one topic. The knowledge points examined are generally the main knowledge points, such as Lenz's law, Ampere's force, induced electromotive force, left-handed rule, right-handed rule and so on. Common synthesis topics include dynamics synthesis, function relation synthesis, electric field synthesis, magnetic field synthesis, electromagnetic induction synthesis and so on.
Comprehensive problems are generally difficult, so when doing such problems, we should spend more time analyzing the changes of their movement, stress, work and energy, and apply the basic knowledge of each part to gradually decompose the problems and solve them corresponding to the corresponding knowledge points.
To sum up, the research shows that in order to solve multiple-choice questions quickly, we must make full use of the known conditions provided by the questions, dig deep into the hidden information and create conditions skillfully and organically. We should not only pay attention to the special treatment of standard questions, but also consider the integration and connection of knowledge inside and outside the subject, simplify complex questions as much as possible, and make effective use of examination time, so as to improve examination results.
Second, the experimental questions
There are two experimental questions in physics I of the college entrance examination, and the time for the physical experimental questions should be 8 ~ 10 minutes.
College entrance examination questions are often presented in the form of a mechanical experiment and an electrical experiment. Judging from the college entrance examination in our province in recent years, electrical experiment is the most important. No matter what form the experimental topic appears, its essence is to investigate from the experimental principle. As long as we start from the experimental principle, we can deal with it calmly. Our coping strategy is: proceed from the foundation and the experimental principle, and treat all changes equally. Classify problems and avoid them by analogy.
Mechanical experiment questions are relatively simple student experiments (mainly involving paper tape analysis and synthesis experiments of springs and forces). There are three fill-in-the-blank questions in the air, which are investigated from the aspects of principle, data and error, and may also be the application of a certain physical principle (adaptation of simple calculation questions) and demonstration experiments. No matter which type it is, it should be analyzed in principle, and the time to answer this small question should not exceed 3 minutes.
The electrical experiment mainly analyzes the selection of circuits and instruments from the experimental principle (safety first, sensitivity must be considered), paying special attention to the conversion of four parameters of voltmeter, ammeter, bulb, rheostat and constant resistance, whether the internal resistance of voltmeter and ammeter is certain or about how much (the measured value can be used to process data in the experimental principle, and the approximate value can be used to estimate the selected equipment), the role of constant resistance in the circuit, and the expression to be measured. These were clear before they became targets. (Description and application of various images are also common test sites. The function expressions of various images are generally derived from closed-loop ohm's law and series-parallel law, and then the meanings of slope, intercept and intersection point are analyzed. )
Third, the calculation problem
A ***3 calculation questions, the first calculation question is about 6 minutes, the second is about 10 minutes, and the third is about 12 minutes (students around the undergraduate line can use part of the third time in the first and second roads). There are three kinds of college entrance examination calculation questions in our province: the first is the problem of integrating theory with practice. The second is a comprehensive calculation problem within the scope of mechanics. In the process of studying the motion of objects, it is a synthesis of mechanical problems to investigate kinematics, dynamics and functional relations. The third is to investigate the motion of charged particles in electric and magnetic fields, electromagnetic induction and circuit synthesis. No matter what form of calculation problem, its basic situation can be attributed to the relationship between force and motion. As long as the force and motion are analyzed clearly, we can find out the motion of each subprocess, list the corresponding formulas of each subprocess, and pay attention to the connection points of each subprocess.
The novel model of the scene of the first calculation problem is mostly a pure mechanical problem (linear motion, Newton's law of motion). This kind of problem has a long narrative and many interference factors. When you answer, you must grasp the important information, turn the scene into a physical scene, and then match it with an action sketch. The relationship between velocity, acceleration, displacement and Newton's law of motion, as well as force analysis, should be marked on the sketch. Understand this and then write the answer.
The second calculation problem is probably a comprehensive problem of force and electricity, involving multi-process analysis and calculation (mainly digital calculation). When solving, we must analyze the force and motion of each process and state, and write out the laws and principle equations followed by each process and state. The operation process can be omitted, but the calculation must be careful, because the result of the previous step often affects the trend of the next step. The state or process of a multi-process problem with more information is the starting point of the problem. Finding out the information of process connection points (changes of speed, direction, energy and force) during thinking can also spark thinking.
The third calculation problem is more complicated and comprehensive, but because it is a step-by-step question, you must never give up the first problem (experts point out that the first problem of the third problem is the simplest one of all calculation problems), and students who are more concerned about the book can't give up the second problem. Students with particularly good grades must list the equation of the third question, which may require higher mathematical ability and the final result is not easy to work out.
Coping strategies for calculation problems: ① To examine one's mastery of basic knowledge and basic theory, one must master all kinds of physical phenomena, theories and laws very skillfully in order to correctly analyze problems. For example, there are two parts in mechanics, one is classical mechanics (linear motion, circular motion and Newton's law of motion), and the other is work and energy. The former part is the process and the latter part is the result. The electrical part is nothing more than the formula deformation of the mechanical part. Although the formula has changed, the concrete analysis is similar to that of mechanics. ② Process splitting. Since these big questions are the superposition of some basic phenomena and theories, we only need to separate these processes and knowledge points. After these complex knowledge points are decomposed into small and simple knowledge points, we can easily decompose them one by one.
Examination skills of common calculation problems;
(1) Search information carefully and comprehensively. Carefully examine the topic, and carefully examine some key points in the text and illustrations of the topic. Some information should be obtained not only from the text of the topic, but also from the attached drawings of the topic, that is, the information of the topic should be collected from multiple angles and cannot be omitted.
② Speak like a book and grasp the key information. So-called? Talk about words? That is, when reading a topic, repeatedly scrutinize the key words in the topic, correctly understand the physical meaning expressed, form a clear physical picture in your mind, establish a correct physical model, and form a way to solve problems. For those keywords that are easy to misunderstand, such as? Variation? With what? Rate of change? ,? How much has it increased? With what? How much has it increased? , showing extreme situations? Just right? 、? Just okay? 、? Most? 、? At least? Wait, pay special attention, it is best to make a mark in the exam.
(3) Thoroughly scrutinize and excavate hidden information. Repeated reading and examination of questions should not only combine the overall situation, but also repeatedly scrutinize, dig out some hidden information from the lines of the questions, and use these hidden information to sort out the problem-solving ideas and establish auxiliary equations.
(4) Distinguish grades and eliminate interference information. Interference information is often mixed with the necessary conditions to solve the problem. If we don't identify it in time, we can easily go astray. Only by boldly abandoning interference information can we solve the problem smoothly.
⑤ Think deeply and analyze key information. Critical state is the mutation point of physical process. Because of its flexibility, concealment and various possible conclusions, it will lead to wrong solutions and missing solutions in physical problems. Therefore, when solving this kind of problem, we should investigate the meaning of the problem, fully restore the physical situation and physical model of the problem, find the turning point, grasp the physical quantity connecting the past and the future, and determine its critical value.
For all the questions of physics in NMET, it can be summarized as follows: stress analysis is the premise, standard drawing is the key, subject accomplishment should be possessed, exercise flow should be clear, critical state should be grasped, examination tools should be prepared, psychological adjustment on the spot should be good, and the score of firm belief should be high.