在初中三年级的物理教学中,遇到用电器的额定电压小于电源电压的问题,为了让用电器正常工作,必须串联一只适当大小的电阻器。关于电阻器阻值大小的计算,学生是比较容易掌握的。关于电阻器所需的电功率,往往被忽略,即使老师讲解了,不少学生往往还是处于似懂非懂状态。为此,我们购了五只阻值均为20Ω,电功率分别为1/8W,1/4W,1/2W, In the third grade physics teaching of junior high school, the problem that the rated voltage of the electrical appliance is less than the power supply voltage is encountered. In order to allow the electrical appliance to work normally, an appropriate size resistor must be connected in series. With regard to the calculation of the resistance value of the resistor, the student is relatively easy to grasp. The electric power needed for the resistor is often ignored. Even though the teacher explained it, many students are still in a state of non-understanding. To this end, we purchased five resistors each with a resistance of 20Ω and an electric power of 1/8W, 1/4W, and 1/2W, respectively.