在初中科学竞赛的培训中,对于同一道习题的二次开发在学生思维拓展的培养中起着至关重要的作用.对于同一道习题的二次开发存在很多的角度,可以从习题的一题多解入手,可以从习题的归纳总结经验开始,也可以从习题的变式改编做起.接下来笔者就根据自身经验,以一道电学竞赛题为例,与大家交流探讨.原题如图1所示的电路中,已知R1、R2、R3和R4的阻值 In the junior middle school science competition training, the secondary development of the same exercise plays an important role in the cultivation of students’ thinking development.There are many angles for the secondary development of the same exercise, More solutions to start, you can learn from the experience summed up the lessons learned, but also from the exercise of adaptation variants start. Then I based on their own experience to an electrical contest title, for example, to discuss with you. In the circuit shown, the resistances of R1, R2, R3 and R4 are known