初中物理教材第二册“用电常识”一章中一个小实验,1983年版电路如图1所示,1984年版电路如图2所示。按照安全用电规则,电路安装应是火线零线并排走,零线安装在下头,开关安在火线上,通过开关进灯头。图1和图2虽然都能达到楼上楼下控制 Junior Physics textbook second volume “electricity common sense” a small experiment, the 1983 version of the circuit shown in Figure 1, 1984 version of the circuit shown in Figure 2. In accordance with the rules of safe power consumption, the circuit should be installed along the zero line FireWire, zero line installed in the next head, the switch on the fire line, through the switch into the lamp. Although Figure 1 and Figure 2 can reach upstairs and downstairs control