Middle school physics experiment report

Learning steps and methods of physical experiment


Middle school physics experiment is one of the main courses to cultivate students' scientific observation, experimental ability, scientific thinking, analysis and problem solving ability. As Mr. Li Zhengdao said: "It is important to teach students to understand the truth..." According to the purpose of physics teaching in middle school and the basic requirements of the syllabus, students should be in scientific experiments in the teaching process of middle school physics experiments. The basic method has a real feeling, thus cultivating their exploration spirit and creativity, and being educated by scientific methods.

1. experimental design

In order to achieve the intended purpose of the experiment, it is necessary to understand why this experiment is to be done. To do this experiment is to solve the real technical problem, the knowledge problem, or to explore the physical phenomena that will appear in the textbook. What is the solution to the actual problem? When exploring the knowledge problems in the book, you should understand which problem and what phenomenon. The purpose is clear and it is the premise of the success of the experiment.

The basic methods of designing experiments are summarized as follows:

Balance method. Used to design measuring instruments. Use a known amount to test and measure other physical quantities. For example, balances, spring scales, thermometers, hydrometers, etc.

Conversion method. Indirect measurement is carried out by means of mutual conversion of force, heat, light and electric phenomena, such as the design of a dot timer, the design of an electromagnetic instrument, a photocell, and the like.

Magnification method. The principle of superposition, reflection, etc. is used to amplify a small amount into measurable, such as a ruler gauge, a spiral micrometer, a Coulomb twist scale, and an oil film method to measure the molecular diameter.

2. Topic for exploratory experiments

Exploratory experiments by students are not intended to reveal physical laws that have not yet been recognized. Rather, after experiencing the whole process of the experiment, it has a real feeling for exploratory experiments, and masters the basic methods of exploring unknown physical laws.

The topic of exploratory experimentation should be compatible with the student's knowledge level and learning tasks. The following points should be noted in the selection of topics:

According to the mathematics knowledge learned by middle school students and the limitations of experimental time, the empirical formula of experimental results is suitable for linearity. Such as:

Physical experiment report · chemical experiment report · biological experiment report · experimental report format · experimental report template 1 linear relationship: Y = a + bx

2 inverse ratio relationship: Y=a+b/x

3 power relationship: Y=axb

Straighten: logy=loga+blogx

4 index relationship: Y=aexp

Straighten: Iny=Ina+bx

In the above formulas, x is an independent variable, y is the number of strains, and is measured at the same time, a and b are constants.

The variation characteristics between the two measurements are highly observable.

The theoretical analysis of empirical formulas should not be too complicated.

3. Physical experiment method

Operational ability mainly refers to the use of basic instruments and the reading of data, the assembly or connection of instruments and equipment, and the elimination of faults.

The role of the basic instrument. The basic measuring instruments involved in middle school physics experiments are: meter ruler, caliper, spiral micrometer, balance, stopwatch, spring scale, thermometer, barometer, ammeter, voltmeter, variable resistance box, multimeter, oscilloscope.

The specification requirements for using basic measuring instruments are:

1Understand how to use the measuring instrument, and specify the allowable limits and precision of the measuring range;

2 For some instruments, such as electric meters, before using, you must adjust the zero point, or write down the zero error;

3 Remember to use rules and operating procedures;

4 read the data correctly.

For example, the correct use of the spring balance is: clear the measurement range of the spring scale; before the measurement, write down the zero point error; when using the spring balance, the direction of the force should be on the same line as the axis of the spring, and the spring balance should not be subjected to force for too long, so as to avoid Causes elastic fatigue, damages the instrument; correctly observes the readings, when recording the data, not only records the number that the minimum scale can indicate, but also reads an estimated number, and the unit must be written after the data.

For example, the correct use of the ammeter is: clear range; before use, adjust the zero point; the correct connection should be connected in series with the circuit to be tested, and pay attention to the positive and negative polarity; read the data correctly, indicate the unit.

Assembly or wiring of instruments and equipment. To perform a physical experiment, it is always necessary to assemble the various instruments, components, and equipment first, and to require that the assembly and wiring must be correct. The specific requirements are: the layout should be reasonable, and it should be easy to observe and operate; the connection should be correct and simple; check before the experiment and make preparatory adjustment if necessary.

For example, in circuit experiments, the operational requirements are:

1 According to the experimental principle circuit diagram, arrange the layout of the instrument and components, to facilitate the connection, easy to check, easy to operate, easy to read data.

2 correctly connect the circuit.

Whether the ammeter and voltmeter are connected in series and parallel with the circuit to be tested, whether the positive and negative polarity are correct; whether the wiring of the sliding line varistor is reasonable; whether the connecting line meets the first branch, then juxtaposed, the rear trunk, and finally the power supply. Program; whether the key can control the circuit; whether the wiring is simple and firm.

3 Check the circuit before the experiment, find the problem corrected in time, and make preparatory adjustments.

4 strictly operate according to the operating program, for example, change the resistance of the resistor, whether it is small to large, or from large to small, and finally, read the data correctly.

Troubleshooting

The troubleshooting in the experiment is not only an operation ability, it involves the mastery of the experimental principle, the method of analyzing the problem, the understanding of the working condition of each component, etc., is a comprehensive application ability.

When the experiment fails, it should be checked one by one according to the working state of each component and the analysis of the joints of each component, so that the fault is finally eliminated.

In short, cultivating experimental operation ability is the necessary foundation for learning physics. It is conducive to the understanding of knowledge, is conducive to creating conditions for exploring problems, and is conducive to the development of students' intelligence.

In physics learning, the ability to cultivate operations should be carried out in a planned and phased manner.

First, the cognitive stage of operation

Requires a preliminary understanding of the operational skills, forming an image of the operation in the mind, requiring simple orientation training according to the prescribed procedures;

Second, the stage of operation

It is required to practice the operation repeatedly to improve the accuracy and coordination of the operation.

4. Observations in physical experiments

Observation is a careful examination and understanding of things and phenomena. It is the perception of thinking, the gateway and source of intellectual activity. The observation in the middle school physics experiment is a purposeful, planned and relatively long-lasting thinking consciousness. Generally, it is necessary to focus on the basic instruments of the experiment, the experimental equipment and devices, the various physical phenomena and data, images and charts in the experiment. , as well as the teacher's normalization operations and so on.

Observe the scale of the instrument. The observation of the instrument scale is mainly to find out the unit of the scale value and its minimum division value, thereby determining which one the measured value should be estimated.

Observe the construction of the instrument. Mainly through observation, understand the structural principle of the instrument, the role of each component, the measurement range and so on.

For example, liquid thermometers are made using the principle of liquid thermal expansion and contraction. They have a glass bubble at the bottom and a glass tube with a closed top end and a thin and uniform inner diameter. There is a proper amount of liquid in the tube and the bubble. The tube is marked with a scale. When the temperature changes, the liquid is hot. The expansion and contraction, the position of the liquid level in the tube changes, and the temperature value can be read from the scale reached by the liquid. The thermometer has different measurement ranges due to different purposes. For example, the measurement range of the thermometer is 35 to 42 ° C, and the measurement range of the general laboratory mercury thermometer is 20 to 100 ° C.

Observe the nameplate of the instrument. The instrument name, specifications, usage and conditions of use can be found by observing the nameplate of the instrument.

For example, some varistor names are marked with a "sliding rheostat, 1.5A50Ω means that the maximum current allowed by the sliding rheostat is 1.5A, and the maximum resistance is 50Ω.

Observe images, charts, schematics, and physical maps. The observation of the image is mainly to observe what physical phenomena it reflects, how the physical quantity changes, and what laws follow the changes in physical quantities.

Observe the chart, mainly by observing the meaning, use, application conditions and units of the listed physical quantities.

For example, the boiling point table of a liquid reflects the temperature at which different liquids boil. It can be used to find the boiling point of a liquid in °C. The boiling point of the liquid is related to the pressure, etc. The conditions listed in the table are usually at 1 standard atmosphere. The boiling point value.

Observing the schematic diagram, circuit diagram, physical diagram, etc., mainly observe what physical model they reflect, what use, how the structure of the instrument and circuit is laid out, how the various components are connected, what is the relationship between the parts, and so on.

Observe the installation of the experimental setup. Through the observation of the installation of the experimental device, the purpose of the device, the instruments and components used, the order and method of the instrument configuration, and the like can be understood.

Observe the operation of the experiment. By observing the experimental operation process, you can understand what preparations need to be done before the operation, and the sequence and process of the operation experiments.

Observe the phenomenon of the experiment. The observation of experimental phenomena is mainly to observe the conditions and processes of the phenomena.

For example, two parallel wires that are very close together will attract each other when a current in the same direction is passed; when they flow in opposite directions, the two repel each other.

Observe the data of the experiment. The observation of the experimental data requires that the method of observation should be correct. The digital reading should reach a certain accuracy according to the minimum scale of the instrument. When recording the measurement results, the unit of the data must be clarified.

For example, when measuring the length of the object, when observing the scale, the eye should face the system line, and the squint should not be squinted. When observing the scale of the water surface in the glass cylinder or the glass measuring cup, the line of sight should be flush with the bottom of the concave surface of the water surface. When observing the mercury thermometer, The line of sight should be at the same level as the highest point of the mercury surface.

Observe the teacher's demonstration. Observe the teacher's demonstration demonstration, observe the teacher's standardized installation experimental device, reasonably arrange the experimental program and correct operation process, and demonstrate physical phenomena, data reading and recording, how to get experimental results, and so on.

5. Observation method in physical experiment

Physical experiments, commonly used methods are: comparative observation and inductive observation.

Comparative observation. People know things and phenomena, often by comparing the comparison of two things and phenomena, or comparing the situation before and after the change of a certain phenomenon.

For example, by observing the volume change during melting or solidification of the substance, the paraffin wax can be placed in a beaker, and the alcohol lamp is slowly heated to completely melt it. At this time, it was observed that the paraffin level was level, indicating the height at which the liquid level contacted the beaker. After removing the alcohol lamp and waiting for the paraffin to cool down, it was observed that the height of the paraffin wax contact with the beaker did not change significantly, but the surface was concave.

For example, when learning boiling, you can observe the situation of the liquid before boiling and boiling, and compare. At this time, students are required to observe carefully, agilely, comprehensively and accurately. As a result, it is found that before boiling, bubbles are formed inside the liquid, and the bubbles gradually become larger during the ascending process, and rupture after reaching the liquid surface. By comparing the conditions before and after the liquid is boiled, it can be known that boiling is a phenomenon in which both the inside and the surface of the liquid are vaporized violently.

We can also artificially control the conditions to make the liquid boil under normal pressure, pressure and decompression, and compare the boiling phenomenon under different conditions. It can be known that the boiling point of the same liquid changes with the external pressure; if the research object is different liquid They are allowed to boil under the same external pressure conditions. It can be seen from comparative experimental observation that the boiling points of different liquids are different under the same pressure.

It can be seen from the above two examples that the use of contrast observation is conducive to grasping the characteristics of the phenomenon and its difference from other similar phenomena.

Inductive observation. Inductive observation is usually used when summarizing the general laws of some phenomena, reflecting the essence of the phenomenon, or studying some problems involving more variables. That is, by observing individual phenomena separately, some individual conclusions are obtained, and then analyzed and summarized, and the general law is obtained.

For example, in order to facilitate the study of the relationship between the acceleration of the particle and the force and mass, the relationship between the acceleration and the force is observed under the condition that the mass is determined first; then another factor is determined - the force is constant. In the case, observe the relationship between acceleration and mass; finally, by inducting Newton's second law of motion.

It can be seen that the use of inductive observation is conducive to grasping the essence of the phenomenon and studying the general law of more complex phenomena.

In short, to cultivate observation ability, we must clearly observe the purpose and task of observation, stimulate students' interest in observation, and enable students to develop habits that are good at observation and diligent thinking. They should teach students how to observe, observe and train students, and ask for observation. Accurate, comprehensive, detailed and agile.

6. Representation of experimental results

The representation of the experimental results first depends on the physical mode of the experiment, and the representation of the experimental results is considered by the correlation between the measurements. The common experimental results are represented by graphical methods and equation representations. When processing the data, you can choose any method to represent the final result of the experiment as needed and convenient.

Graphical representation of experimental results. The experimental results are represented by functional graphs, which also have universal practical value in experimental work. It has obvious intuition and can clearly reflect the changing process and the trend of continuous change between variables during the experiment. Accurately draw the graph, and also graphically if the specific mathematical relationship is unknown, and use the graph to select the mathematical model of the empirical formula. Therefore, using graphics to represent the results of the experiment is something that every middle school student must master.

The main problem with the graphical method is the fitting of the upper line, which can generally be carried out in five steps.

1 Organize the data, that is, take a reasonable number of significant digits to represent the measured value, eliminate the suspicious data, and give the corresponding measurement error.

2 Select the coordinate paper, the selection of the coordinate paper should be based on the principle of facilitating the drawing or more reflective of the relationship between the variables. Different coordinate papers can be selected according to needs and conveniences. The two variables that originally belong to the curve relationship can be converted into a linear relationship by using the logarithmic coordinates after coordinate transformation. Commonly used are rectangular coordinate paper, single logarithmic coordinate paper and double logarithmic coordinate paper.

3 coordinate division, after the selection of the coordinate paper, it is necessary to determine the value represented by the distance of each small grid on the drawing, but at least the following two principles should be noted:

a. The size of the grid value should be compatible with the accuracy of the measured values.

b. In order to facilitate the drawing and use the graphic to find the valid digits represented by each grid value, try to use 1, 2, 4, and 5 to avoid using digits such as 3, 6, 7, and 9.

4 as a scatter plot, according to the determined coordinate scale value, the data is marked as the coordinates of the point in the coordinate paper. Considering the classification of the data and the sequence of the measured data sets, the coordinates of the points should be marked with different symbols. Commonly used symbols are: × ○ ● △ ■, etc., the center of the mark is the coordinates of the data.

5 Fitting curve, fitting curve is the main purpose of graphically representing the experimental results, and also a key part of cultivating students' mapping methods and techniques. Pay attention to the following points when fitting curves:

a. The number of turning points should be as small as possible, and no artificial bending can occur.

b. The curve should be as close as possible to each coordinate point, not through all points.

c. The number of points on either side of the curve should be similar except for the point through which the curve passes.

6 Note: The specification of the mapping method indicates that the experimental results should be necessary to explain the obtained graphics. The contents include the physical definition represented by the graphics, the method of viewing and using the graphics, the time, location, and conditions of the graphics, and the source of the graphics data. Wait.

The equation representation of the experimental results. The equation is a mathematical form that is used by middle school students. The equation is used to express the experimental results. Not only is it compact in form, but it is also convenient for further processing in mathematics. The equation representation of the experimental results can generally be divided into the following four steps.

1 Establish a mathematical model. For an experiment that only studies the relationship between two variables, the mathematical model can be determined by means of a graphical method. First, according to the experimental data, the corresponding line is made in the Cartesian coordinate system to see if the line is a straight line or an inverse ratio. The relationship curves, power function curves, exponential curves, etc., can be used to determine the mathematical model of the empirical equation:

Y=a+bx, Y=a+b/x, Y=a\b, Y=aexp

2 straightening, for the convenience of the undetermined coefficient of the curve relationship equation, in the case of less precise requirements, on the basis of the determined mathematical model, through the logarithm method of the mathematical model, transformed into a linear equation, and according to The experimental data uses a single logarithmic coordinate system to make a corresponding line graph.

3 Find the undetermined coefficient of the linear equation. According to the straight line graph after straightening, through the principle of analytic geometry that the student has mastered, the slope and intercept can be found according to the straight line in the coordinate system to determine the two undetermined coefficients of the linear equation.

4 Find the empirical equation, and substitute the two undetermined coefficients determined into the mathematical model, that is, obtain the empirical equation of the Cartesian coordinate system that the middle school students are more accustomed to.

Middle school physics experiment has its set of experimental knowledge, methods, habits and skills. To learn the experimental knowledge, methods, habits and skills of this system, teachers need to make scientific arrangements in the teaching process, from shallow to deep, from simple to simple Train and train. Gradually master the basic methods of exploring unknown physical laws.

7. Group experiment problem

The main problems existing in the group experiment are: 1 Some students do not ask whether the purpose of the experiment is achieved, and do not experiment according to the experimental rules and experimental procedures, just in the laboratory, the instrument is played as a toy indiscriminately. 2; some students do not abide by the discipline of the laboratory, string in the laboratory, speak loudly, interfere with other people's experimental operations; 3 in the group experiment is often carried out by one person, the rest of the students just sit Can not participate in experimental activities; 4 some students do not pay attention to the scientific nature of the experiment, do not pay attention to the authenticity of the experimental phenomenon and experimental data, but to make up the experimental data, and turn the experimental class into a class of materials and conclusions. In view of the above situation, in organizing group experiments, especially when entering the laboratory for the first experiment, the pre-experiment education began to cultivate good experimental habits from the beginning. If you care for the instrument, follow the various disciplines of the laboratory, and clarify the purpose of the experiment, the experimental principle, the experimental procedure, the precautions during the experiment, and the operation and placement of the experimental instrument before the experiment. For example, the placement of the experimental instrument should be easy to operate and easy to observe. The instruments and instruments that need to be observed and read should be placed close to the operator in the middle. The instruments and instruments that need to be adjusted should be placed slightly to the right in front. Other devices do not affect the operation. Prevent observations from being placed in an orderly manner. Students should be required to participate in experimental activities, carefully observe experimental phenomena and record real experimental data. After the experiment is finished, the experimental instrument is cleaned up to the reduction site. Carefully deal with the data measured by the experiment, analyze the phenomena observed in the induction experiment, and draw the experimental conclusions, analyze the experimental error, and write a simple experimental report.