Senior high school physics Lenz law teaching plan 1
I. teaching material analysis
Faraday's law of electromagnetic induction and Lenz's law are important laws in electromagnetism. One determines the magnitude of the induced electromotive force and the other determines the direction of the induced current. They are interrelated, reflecting the diversity and complexity of electromagnetic induction laws.
Lenz's law is the projection of electromagnetic induction, which exists objectively and develops and changes. Since it is a law that shows the essence of things, it is called law in physics. From the new curriculum standard, it is the best starting point to embody the specific curriculum goal of "process and method".
The textbook points out the direction of teaching, so that students can experience the process of scientific inquiry, understand the significance of scientific inquiry, and try to study physical problems and verify the laws of physics by scientific inquiry. However, in the details and process of exploration, teachers and students are left with a broad space for thinking and design, which is helpful to stimulate new thinking, discover new methods, ask new questions, draw new conclusions and embody the new curriculum.
Judging from the content of the textbook, Lenz's law transforms the concept of "field" in students' knowledge from "static field" to "dynamic field", and it involves many physical quantities and complicated relations, which brings great difficulties to teaching.
Lenz's law is an important law of electromagnetism, which is the theoretical basis for students to analyze and solve electromagnetic problems in the future. The college entrance examination questions are often expressed in the form of comprehensive questions, which require students to apply them flexibly.
2. Analysis of learning situation
Students have been exposed to the knowledge of electromagnetic induction in junior high school, but it is still very superficial, especially the judgment of the direction of induced current has not been studied. This textbook tries to summarize the general law of judging the direction of induced current in electromagnetic induction through students' own inquiry.
For a long time, in the process of education and teaching, teachers and students have equal status, people-oriented, and adhere to the dominant position of students and teachers.
This class is a regular inquiry class, which presents students with phenomena, problems, not conclusions. Influenced by exam-oriented education, students will remember the conclusion by telling the content of the class before class. Mechanical and scripted cooperation with teachers in class can't achieve the teaching purpose without in-depth thinking, so students don't need to preview this class.
Faced with new phenomena and problems, there is no single fixed answer, and students have a strong desire to explore, which provides more space for their thinking divergence. On the other hand, the content, mathematical operation and physical theory of this section are not high, which appropriately reduces the learning difficulty. Choosing inquiry teaching is the best way.
Inquiry teaching attaches importance to the process and method of inquiry, not the conclusion. Inquiry process is a hotbed of creative thinking. Paying too much attention to the results may lead to the loss of enthusiasm for inquiry and stifle students' desire for inquiry.
Three. Teaching objectives
Knowledge and skills
A) The relationship between induced current and magnetic flux change is obtained through experimental exploration, and the content of Lenz's law will be described.
B) Understand the meaning of the word "obstruction" in the content of Lenz's Law and feel the ways and means of "magnetic flux change" through the replay analysis of the experimental process.
C) Through the intuitive comparison of experimental phenomena, it is further clear that the process of induced current generation can still follow the laws of energy conversion and conservation.
Process and method
A) Observe the experiment and experience the direction of induced current in electromagnetic induction.
B) Try to design an indication scheme for the direction of induced current by using the knowledge learned, and do experiments.
C) Pay attention to the individuality of experimental phenomena, find out the characteristics of experimental phenomena, sum up the laws, and cultivate students' abstract thinking ability and innovative thinking ability.
Emotional attitude values
Enthusiasm: gradually accumulate enthusiasm for inquiry in the process of experimental design and operation, and cultivate students' spirit of being brave in inquiry;
Participation: form a good study habit of actively participating in scientific research;
Communication: We can cooperate with each other, encourage each other, make friendly comments and live in harmony in a free, open and equal space for exploration and communication.
Philosophical thinking: be able to understand Lenz's law from the perspective of causality and contradiction;
Four. Teaching emphases and difficulties
Emphasis: experimental design of Lenz's law and summary of experimental results.
Difficulties: the relationship between the magnetic field excited by induced current and the original magnetic field.
Understanding of the word "obstruction" in the expression of legal content.
Verb (abbreviation of verb) design concept
According to the characteristics of students, this lesson has made in-depth exploration and thinking on the content of teaching materials. Prepare teaching materials, prepare students, prepare teaching methods, always put students in the main position of teaching, let students participate, let students design, create a "safe" teaching environment, open the way, and make students' thinking and teachers' guidance vibrate.
The whole class mainly adopts the "discovery method" advocated by Bruner, sums up the content of Lenz's law by combining experimental exploration, puts the process and method of drawing the law in the first place, and puts the students' emotional value experience in an important position. The overall teaching layout is as follows:
Shape merging format
Teaching process of intransitive verbs
(A) the introduction of experiments, arouse students' guesses and assumptions, and stimulate students' desire to explore.
Teacher: In the experiment of exploring electromagnetic induction, you may notice that the direction of induced current is different under different conditions. Let's repeat the last experiment
Teacher (demonstration): When the magnet is inserted into the solenoid and pulled out from the solenoid, the pointer of the sensitive galvanometer swings back and forth from left to right.
Teacher: Have you noticed that when I insert the magnet into the solenoid and pull it out, the induced current in the circuit has different directions? So, what factors determine the direction of the induced current? What rules do you follow? Let's guess through the above experiment.
Health: It may be related to the winding direction of coil wire, the direction of original magnetic field and the changing direction of original magnetic flux.
Teacher: We use experiments to explore and verify everyone's guesses.
(B) learn new knowledge and start the process of experimental inquiry.
1. Students do experiments and make their own coils to find out the winding direction of the coil wires.
Teacher: Students think that the direction of induced current is related to the winding direction of the coil, so it is necessary to find out the winding direction of the coil. Using ready-made coils, it is sometimes difficult to find out the winding direction of wires due to other reasons such as loose wires. Let's start winding the coil ourselves, which will help us understand the winding direction of the coil conductor. "It's too shallow on paper, but I don't know how to do it."
Group experiment: (divided into 6 groups, each group chooses the group leader, recorder and reporter, and pays attention to cooperative inquiry)
Experimental preparation: a plastic pipe with a length of about 20 cm (sawed at both ends); A wire about 2 meters long.
Student activities: Students wind the coil by themselves under the guidance of the teacher.
2. Under the teacher's inspiration, complete the teaching design in the current direction.
Teacher: The coil is finished. What problems do we need to find out?
Health: Indicates the direction of induced current.
Teacher: How to guide? What experimental equipment can be used?
Student: The student's answer may be the following two situations:
A: When there is no current, the pointer is in the center of the dial. When the current flows in from different terminals, the deflection direction of the pointer is different. We can judge the input direction of current according to the deflection direction of the pointer.
B: Using the unidirectional conductivity of light-emitting diodes, connect the diodes in series in a closed loop. When the diode emits light, it shows that the direction of induced current is consistent with the shunt direction of the diode.
Embedded brush
(Students' knowledge has been applied, and their abilities have been reflected, thus generating enthusiasm for learning. )
Teacher: What kind of circuit should be designed to find out the relationship between the current direction and the terminal of the meter, or the relationship between the current direction and the diode light emission?
Student activities: (students communicate with each other, complete the design together, and give appropriate feasibility evaluation to different results)
Teacher: (Find the best and reasonable design from the classmates' designs) As shown in the figure: shape MERGEFORMAT.
Teacher: Connect the circuits according to the designed scheme, determine the indicated direction and give a brief explanation.
Teacher: The direction of current can also be judged by light-emitting diodes, which are conductive, emitting light in the forward direction, not energized, and emitting light in the reverse direction.
3. Teacher-led, complete the experimental scheme design and data collection.
Teacher: We need to study the direction of induced current. What should we do next?
Health: Turn on the closed loop, let the magnetic flux change, produce induced current, and indicate it with corresponding instruments.
Teacher: What scheme can be designed to realize it?
Student: (AC interaction, according to the electromagnetic induction phenomenon, the two most likely designs are shown in the following figure)
Shape merging format
Teacher: Please use the equipment in the group, choose a circuit, connect the equipment and record the experimental results.
(Two programs, two study plans)
Senior high school physics Lenz law teaching plan II
1. teaching material analysis?
Is Lenz's Law an optional course in physics for senior three to senior two? The emphasis and difficulty of the chapter "Electromagnetic Induction" involve many elements and have complicated relations (magnetic field direction, flux change, coil winding direction, current direction, etc.). ), its law is hidden, abstract and general. Therefore, it is difficult for students to understand Lenz's law, which has become a difficult point in teaching this chapter. The main task of this lesson is to guide students to sum up the general law of the direction of induced current-Lenz law through the process of experimental inquiry, and have a preliminary understanding of the content of this law. The teaching content of this section is based on the second section "Exploring the conditions of electromagnetic induction". Although all the experiments in the textbook have been done in previous teaching, it is necessary to re-study the experiments of two students in the second quarter from the perspective of determining the direction of induced current. Lenz's law is of universal significance for judging the direction of induced current and understanding the law of energy transformation in electromagnetic induction, and it is also helpful for understanding the right-handed rule. The college entrance examination description belongs to the second-level requirement. ?
Second, the teaching objectives
? 1, knowledge and skills:?
(1) Understand the content of Lenz's law. ?
(2) The direction of induced current can be preliminarily determined by applying Lenz's law. ?
(3) Understand that Lenz's law is the reaction of the law of conservation of energy in electromagnetic induction. ?
(4) Understand the meaning of the word "obstruction" in Lenz's Law.
? 2. Process and method?
(1) Through observation and demonstration experiments, the general law of induced current direction is explored and summarized. ?
(2) Through experimental teaching, feel the experimental inquiry process of Lenz's Law, and cultivate students' ability to observe experiments, analyze, summarize and summarize physical laws. ?
3. Emotional attitudes and values?
(1) It is an important scientific method to make students learn to know the commonness of general things from the individuality of individual things. ?
(2) Cultivate students' spatial imagination. ?
(3) Let students participate in solving problems and cultivate students' scientific inquiry ability and cooperative spirit. ?
3. What are the teaching emphases and difficulties?
Emphasis: Understand Lenz's Law and use it to judge the direction of induced current.
Difficulties: Lenz's Law? Understanding of "hindering change" ?
Fourth, the analysis of academic situation?
Our students are in the last grade of seven senior high schools in the city, and their mathematical ability is generally weak and their understanding ability is poor. In each class, students' existing knowledge level and experimental ability are different. This requires us to thoroughly understand the teaching materials, be familiar with the learning situation, fully tap the maximum potential of information technology, and at the same time integrate physics teaching in senior high school with the help of physics experiments and prepare teaching methods. Through the teaching of "Exploring the conditions of induced current generation" in the last section, students have a clear understanding of the conditions of induced current generation. In this lesson, the direction of induced current is explored in detail. Students' experimental ability, language expression ability and teamwork ability can be well exercised. ?
Verb (abbreviation of verb) teaching method?
? 1.？ Experimental method: the teacher demonstrates the experiment? Student experiment. 2. Learning plan problem-oriented teaching method
Sixth, experimental preparation
1. Students' learning: tutoring plan, students' experimental equipment. ?
2. Teachers' teaching: making multimedia courseware, previewing learning plans before class, exploring learning plans in class and designing problems. ?
3. Design and layout of teaching environment: cooperative learning in groups, divided into 6 study groups. ?
Seven, the teaching process?
( 1)? Check the preview and answer questions.
Check the implementation to understand the students' preview, find students' doubts, and make the teaching targeted. ?
1, scene import display target?
Create a scene?
The video introduces the new technology of electromagnetic induction; Improved experiment of Lenz's law demonstrator: demonstrate the experiment of magnet passing through aluminum tube. ?
Questioning questions? :?
Why do eq oac(○, 1), closed aluminum ring and open aluminum ring produce different movements?
Why don't eq oac(○, 2), ferromagnetic ball and iron ball land at the same time after passing through the aluminum tube?
2. Introduce the problems of experimental construction.
Are the pointer deflections the same when eq oac(○, 1) and magnets are plugged in and out? What do you mean by left leaning and right leaning?
Are the pointer deflection of Eq oac(○, 2) and ammeter regular?
Eq oac(○, 3), what method should be used to find the direction of induced current?
3. Determine the theme and plan?
Eq oac(○, 1) and pointer deflection indicate that the direction of current is different, so what is the relationship between the direction of current and pointer deflection?
Eq oac(○, 2), guess what factors are related to the direction of induced current.
(1) is related to the connection of the coil; (2) It is related to the motion mode of the magnet; (3) It is related to the direction of the original magnetic field; (4)……?
Eq oac(○, 3), make a plan (how to complete the above verification)?
(1), how to obtain the induced current? The research object of this experiment is the closed loop corresponding to the coil. ? (2) Find out the relationship between the deflection direction of ammeter pointer and the current direction. ? (3) Understand the winding direction of the coil, so as to determine the magnetic field direction of the induced current. ? (4) How to choose experimental equipment (5) The direction of magnetic field in the coil, the change of magnetic flux passing through the coil, the direction of induced current and the direction of magnetic field generated by it should be recorded in the experiment. ?
Guide the students to discuss and solve the above problems, and get the theme of this lesson:?
1, what is the relationship between the direction of the current and the deflection of the pointer?
2. How to determine the direction of induced current? And put forward a guess. ?
3. Determine the specific content of the plan?
(1) There are several possibilities for the relative motion between the bar magnet and the coil.
(2) In order to explore the relationship between the direction of induced current and the change of magnetic flux and the direction of primary magnetic field, what methods are commonly used in physics to control the sequential method of variables?
(2) Cooperative inquiry and intensive teaching. ?
Inquiry 1: Study the direction of induced current?
(1), exploration target: What factors are related to the direction of induced current? ?
(2) Exploration direction: Starting with the magnetic effect of magnets and coils. ?
(3) Exploration means: group experiment (equipment: solenoid, sensitive galvanometer, bar magnet, wire)?
(4) the inquiry process? : See Figure 4.3-2 of the textbook P 10 for details.
? (Experiment record, completion form)
When the N-pole S-pole magnet is stationary in the tube, the magnet is inserted and pulled out when it is stationary in the tube. N is next? S is next? N is next? S drops in the direction of the lower primary magnetic field B? Up, up, down? Up? Come down? Does the change of upward primary magnetic flux φ increase? Less, more, less? The same? The same? The direction of the magnetic field b with constant induced current? Up, down, down, up, up, no, no, no, no, no,no. The directional relationship between the primary magnetic field B and the magnetic field B of the induced current is opposite, the same, but the same. (5) Students discuss in groups.
Senior high school physics Lenz law teaching plan daquan III
First, teaching material analysis:
The teaching content of this class is the textbook of People's Education Press, and senior high school physics elective 3-2 "The direction of induced current-Lenz's law", chapter 1, section 3. ? Lenz's law is an important part of electromagnetic induction law. Like Faraday's law of electromagnetic induction, it is also a teaching focus in this chapter and one of the two important pillars for analyzing and dealing with electromagnetic induction.
Because this law involves many physical quantities and laws, only by correctly judging the direction of the original magnetic field, the change of the original magnetic flux, the magnetic field direction of the induced current and the ampere rule can we get the correct direction of the induced current. At the same time, students must be able to correctly use Ampere's Rule, Left-handed Rule and Ampere's Rule to solve problems, so this part is also the difficulty of the electrical part.
Second, the difficulties in teaching:
Teaching emphasis: understand the relationship between the direction of induced current and the change of magnetic flux that causes induced current.
Teaching difficulties: according to the teaching objectives, carry out experimental design and operation.
Third, the analysis of learning situation:
Students master the concept of magnetic flux and can analyze the change of magnetic flux. The distribution of magnetic induction lines of bar magnets is known. Students have used experimental equipment (magnetic rods, galvanometers, coils, etc.). ) to study the conditions of induced current generation.
Fourth, the teaching objectives:
1. Knowledge and skills?
(1) will show the relationship between the direction of induced current and the change of magnetic flux that causes induced current.
(2) I will use my own language to express the meaning of "obstruction" in "the magnetic field of induced current always hinders the change of magnetic flux that causes induced current". ?
(3) Lenz's law will be used in electromagnetic induction to judge the direction of induced current.
2. Process and method
(1) Through the inquiry process, we can understand the scientific inquiry elements such as asking questions, guessing hypotheses, making plans, designing experiments, analyzing and demonstrating, and verifying.
(2) Understand the research methods of physics and the role of physical experiments in the development of physics through the learning process of Lenz's law.
(3) Learn to study physical problems by means of experimental inquiry.
3. Emotional attitudes and values
(1) Through Lengci's attention to Faraday's research results and the introduction of the law of the direction of induced current, students' curiosity and thirst for knowledge are cultivated, and the hardships and happiness of exploring the laws of nature are experienced.
(2) Actively communicate and cooperate with others through experiments to cultivate team spirit.
Five, design ideas:
As the teaching of physical laws, this section focuses on guiding students to think and study physical laws by experiments. To this end, this class adopts the operation mode of students' experimental inquiry in groups. Under the inspiration of teachers, students discover and solve problems through their own experimental operations and acquire new knowledge.
In order to break through the difficulties, this course adopts the teaching method of "guided inquiry", and the classroom teaching design is as follows: creating problem scenarios → students discussing and guessing → designing experiments → exploring experiments → (changing demonstration experiments into students' own exploring experiments) → analyzing experimental phenomena → drawing Lenz's law → classroom practice → classroom practice.
In the teaching process, we should grasp the process of knowledge generation, actively guide students to explore actively, and highlight students' dominant position in classroom teaching.
Six, equipment preparation:
Multimedia platform, coil, bar magnet, wire, dry battery, bar magnet, sensitive galvanometer, Lenz's law demonstrator.
Seven, the teaching process:
First, set the scene and introduce the topic.
[Teacher shows the scene]: (Introduce the subject experiment-three comparative experiments)
1. comparative experiment 1: ferromagnetic ball and iron ball are released freely from the same height at the same time.
2. Comparative experiment 2: Free release of ferromagnetic balls and iron balls from the same height through aluminum tubes A and B, respectively.
3. Comparative experiment 3: Free release of ferromagnetic balls and iron balls from the same height through aluminum tubes B and A respectively.
[Students think and answer]:
Do ferromagnetic balls and iron balls land at the same time?
Compared with experiment 1, two balls landed at the same time; In comparative experiments 2 and 3, the two targets did not land at the same time.
[Teacher's inspiration and guidance]:
1. Why didn't the ferromagnetic ball and the iron ball land at the same time after passing through the aluminum tube?
(Learn Lenz's Law in Section 3 of Chapter 4 first)
Second, review the experiment and ask questions.
[Teacher shows the scene]: (Review the introductory experiment)
[Students think and answer]:
1. Observe whether the sensitive ammeter pointer is deflected. In which direction?
Deflection; Left, right.
2. What does the sensitive ammeter pointer deflection mean? What do different deflection directions mean?
Induced current generated in the coil; The direction of that induce current will change.
3. What factors are related to the direction of induced current?
Third, compare experiments and make reasonable guesses.
[Teachers show scenarios]: (Two comparative experiments)
Comparative experiment 1: As shown in Figure (4), N-pole insertion and N-pole extraction.
Comparative experiment 2: As shown in Figure (5), N-pole insertion and S-pole insertion.
[Students think and guess]:
1. What factors may be related to the direction of induced current?
A. The direction of induced current may be related to the change of magnetic flux;
B the direction of the induced current may be related to the direction of the original magnetic field;
[Teacher's inspiration and guidance]:
1. The direction of the induced current may be related to the direction of the original magnetic field and the change of magnetic flux.
2. Let's discuss the relationship between the direction of induced current and the change of magnetic flux and the direction of original magnetic field through experiments.
Fourth, experimental exploration, induction and generalization.
Experimental purposes:
Explore the relationship between the direction of induced current, the change of magnetic flux and the direction of original magnetic field, that is, what law does the direction of induced current follow?
Thinking and discussion:
1. How many possibilities are there for the relative motion between the bar magnet and the coil?
2. In order to explore the relationship between the direction of induced current and the change of magnetic flux and the direction of primary magnetic field, what methods are usually used in physics?
Control variable method
Query scheme:
Sequence control: (1) change of magnetic flux (2) direction of primary magnetic field (3) direction of induced current.
relative movement
? Changes in primary magnetic flux? Original magnetic field direction, induced current direction (top view)?
Determine before the experiment:
1. Relationship between pointer deflection direction and current direction:
Pointer right bias-current flows into the sensitive ammeter from the positive end;
The left bias of pointer current flows into the sensitive ammeter from the negative electrode.
2. Then determine the direction of the induced current in the coil along the lead.
Experimental steps:
1. Relationship between pointer deflection of sensitive galvanometer and current direction.
2. According to the change of magnetic flux, the experiment can be divided into two categories: magnetic flux increase and magnetic flux decrease.
3. Experiment in groups and record the results.
4. The teacher leads the students to fill in the form.
Group exploration:
Collect data:
Seeking "intermediary" induction;
Let students feel that scientists are serious and not afraid of difficulties.
1. What are the conditions for generating induced current?
Summarize and form a conclusion:
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