People can dance on the stage under the light. Can small pieces of paper dance on the plastic board with the accompaniment of music?
Let's do a little experiment. First, we prepare some pieces of paper and a plastic stick, put the paper on the table, rub the plastic stick back and forth many times, and then immediately suck the paper with the rubbed plastic stick. At this time, a miracle appeared. Paper put on beautiful clothes and began to dance. Why?
In fact, this is the role of static electricity. How did static electricity come from? Originally, all substances were made up of molecules, and molecules were made up of atoms. In atoms, there are negatively charged electrons and positively charged protons. Under normal circumstances, the number of protons in an atom is the same as the number of electrons, so it is not charged. Electrons surround the nucleus, and once they are subjected to external force, they leave the orbit and invade other atoms B. Atom A is positively charged due to the lack of electrons, which is called cation, and atom B is negatively charged due to the increase of electrons, which is called anion. The reason for the uneven distribution of electrons is that electrons are off track by external forces, which contain various energies (such as kinetic energy, thermal energy, chemical energy, etc.). ). Any two objects of different materials can be separated after contact, and static electricity can be generated, which is called triboelectrification.
In daily life, we often encounter this phenomenon in dry and windy autumn: when we take off our clothes and sleep at night, we often hear crackling sounds in the dark, accompanied by blue light; When you meet and shake hands, as soon as your fingers touch each other, you will suddenly feel a sharp pain in your fingertips, which is shocking; When I get up in the morning to comb my hair, my hair tends to "float", and the more I manage it, the more chaotic it is. When you pull the door handle and turn on the tap, you will get an electric shock, and you will often make a "bang, bang" sound. This is static electricity generated in the human body, some of which will cause harm to the human body.
Knowing the principle of static electricity, we can try our best to avoid its harm to people, and we can also use this principle to manufacture machinery and equipment to serve people.
The Outline of Basic Education Curriculum Reform (for Trial Implementation) requires cultivating students' independence and autonomy in the teaching process, and guiding students to question, investigate and explore. The curriculum standard clearly points out: "Incorporating scientific inquiry into the content standard aims to shift the learning focus from overemphasis on the inheritance and accumulation of knowledge to the process of knowledge inquiry, from passive acceptance of knowledge to active acquisition of knowledge, and to cultivate students' scientific inquiry ability, realistic scientific attitude and innovative inquiry spirit. "It can also be explained that inquiry teaching in junior high school science classes will replace knowledge-based teaching.
It is better to teach people to fish than to teach them to fish. Experimental inquiry, as a main way of learning and inquiry, plays an important role in the new curriculum teaching. Through the interaction between students and teachers, we emphasize the inquiry of learning and experience the process of acquiring new knowledge and completing the construction of new knowledge through five links: asking questions, analyzing problems, exploring experiments, collecting evidence and writing small papers.
First, ask questions, clear objectives
Asking questions is the first step of experimental inquiry learning, and it is a purposeful, exploratory and creative learning method. Appropriate questions are the premise and guarantee of experimental inquiry, the premise and goal of experimental inquiry.
Where does the material for scientific questions come from? There are three main sources: ① from teachers' research and experience accumulation in teaching materials; (2) Problems or opinions raised or exposed by students in the learning process; (3) Confusion and opinions from production and life practice. Students should be supervised explorers, and teachers should find out and encourage students' inaccurate questions and highlights, and sort them out into good questions with correct views. According to the depth of the questions discussed and the students' initiative, the ways to ask questions can be summarized into three categories: (1) teachers' proposed questions; (2) Teachers and students ask questions together; (3) Students ask questions. No matter what the source of the question is and how it is put forward, the questions raised should be enlightening and exploratory, which can arouse students' interest.
Second, analyze problems, conjectures and assumptions.
It is a brainstorming process to search the original knowledge and experience, form a preliminary understanding of the experimental problem situation and its internal relations, and establish guesses and assumptions about the problem. Guess must be logical, innovative and breakthrough at the same time, and have a preliminary understanding of guess and hypothesis. The scientific methods used are prediction, reasoning and hypothesis formation.
In the teaching process, guiding students to guess is a difficult problem. Scientific speculation is not just speculation, it should be based on certain facts. In this kind of teaching, teachers should guide students to decompose the questions to be guessed and provide some materials for students to discuss and guess around the materials. Teachers should grasp a "degree" when guiding students to guess, and avoid adopting "stocking" teaching, which can neither guide nor guide too much. Inquiry teaching needs to guess, and simple deduction can't get new understanding. The law knowledge obtained by simple induction can only be applied to the same situation as the prototype, and cannot become a universal law. Analogy and association play a pioneering and innovative role in scientific development. In teaching, students can be guided to "guess" according to specific problems and encouraged to guess by analogy and association.
Third, control variables, experimental exploration
According to the questions and conjectures raised, we can find the correct conclusion by means of investigation, interview, consulting materials, on-the-spot investigation, observation and experiment, among which experiment is the basic method and main form of scientific inquiry, one of the basic procedures of experimental inquiry learning mode, the substantive process of demonstrating conjecture and hypothesis, the birthplace of knowledge and an effective means to improve quality. Students participate in the experimental design and operation independently, so that each student can experience and appreciate scientific inquiry activities, stimulate students' interest in learning and learn the methods of scientific inquiry. Through experimental exploration, students have gained rich, primary and innovative new experiences and new insights.
There are many methods to explore, such as controlled variable method, equivalent substitution method, analogy method, model method, simulation method and so on. In experimental inquiry, the control variable method is the most commonly used inquiry method. Control variable refers to a method to explore the relationship between this scientific quantity and the scientific quantity to be studied by changing only one factor at a time and keeping other scientific quantities unchanged.
In the experimental design, we should fully consider the research purpose and the existing instruments and equipment, design a feasible and easy-to-operate experimental scheme, and design the corresponding experimental record table and control quantity. Fully consider the influence of the experimental process on the data, design the experimental steps, and reduce the error at the source as much as possible.
Fourth, observe the phenomenon and collect evidence.
Observing phenomena and collecting evidence is an important implementation process of the experiment. Guide students to collect the evidence needed to solve problems through experimental inquiry, investigation, data consultation and surfing the Internet, obtain information through multiple channels, process all kinds of information through comparison, classification, induction and generalization, screen useful evidence, and express it in the form of charts, essays and investigation reports. Students seek the basis and evidence that can solve problems, deal with relevant information and materials qualitatively or quantitatively, and cultivate the spirit of seeking truth, being realistic and constantly innovating.
Fifth, summarize and write a short paper.