1问题的来源在人教版高中物理选修3-1教材上第69页和第71页上有这样两幅电路图.人教版选修3-1教材第69页上的电路图使用的限流变阻器图形符号明显只连接2根线(如图1),但是,同一节中第71页的电路图中使用的限流变阻器图形符号却分明连接了3根线(如图2).而且,这两幅图都是测量电源电动势和电源内阻的实验电路图,其中变阻器的作用都是作为限流电阻,但是变阻器电路图的画法不一样. 1 The source of the problem is that there are two such circuits on page 69 and page 71 of the PEP High School Physics Elective 3-1 textbook. PEP Elective 3-1 Textbook Circuit diagram on page 69 Current Limiting Rheostat Graphics The symbol clearly connects only two wires (Figure 1), but the current limiting rheostat symbol used in the circuit diagram on page 71 of the same section is clearly connected to three wires (Figure 2). Moreover, the two diagrams Are measured power electromotive force and power supply resistance of the experimental circuit diagram, in which the role of varistor as a current limiting resistor, but varistor circuit diagram drawing is not the same.