恒定电流这一章节在高中物理学习中占有重要地位,学生学习起来比较吃力,常犯一些错误,笔者在教学过程中发现一个小小的易错点,在此提出来,希望对同学们有所帮助.例在如图1所示电路中,闭合开关S,当滑动变阻器的滑动触头P向下滑动时,四个理想电表的示数都发生变化,电表的示数分别用I、U_1、U_2和U_3表示,电表示数变化量的大小分别用△I、△U_1、△U_2和△U_3表示,下 The chapter of constant current plays an important role in the study of physics in senior middle schools. Students are more difficult to learn and often make mistakes. The author found a small error-prone point in the teaching process. Here, I hope to have classmates. In the circuit shown in Fig. 1, the switch S is closed. When the sliding contact P of the sliding rheostat slides downward, the numbers of the four ideal electric meters change, and the numbers of the meters are respectively I, U_1. , U_2 and U_3 indicate that the magnitude of the change in the number of electrical representations is denoted by ΔI, ΔU_1, ΔU_2 and ΔU_3, respectively.