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1.导入新课师:对于如图1的电路,你有哪些方法可以改变小灯泡的亮度?小组内讨论,然后进行交流.图1学生:①改变电源的电压;②串联一个滑动变阻器,然后改变电路中的电阻大小.师:实验验证,观察灯的亮度的变化.问:灯时亮时暗说明什么?生:电路中的电流时大时小.师:电路中电流的大小由哪些因素决定?(创设情境,提出问题)2.猜想与假设师:鼓励学生大胆猜测:你们猜电流的大小究竟由哪些因素决定呢?并说出你猜想的的依据.学生分组讨论,教师适当提示.
1. Import a new class: For the circuit in Figure 1, what are some of the ways you can change the brightness of a small bulb? Discuss in the group and then communicate. Figure 1 Students: ① Change the voltage of the power supply; ② Connect a sliding rheostat in series and then Change the resistance of the circuit size. Teacher: experimental verification, observation of the lamp brightness changes. Q: When the light is dark when the dark explain what? Health: the current in the circuit when large and small. Teacher: What are the current circuit size Decide? (Create situation, ask questions) 2. Conjecture and Hypotheses Teacher: Encourage students to make a bold guess: You decide the current size depends on what factors? And tell you the basis for the guess. Students group discussion, the teacher prompts.