人教版物理选修3-1教材(修订版)的第2章第8节有幅多用电表的电路图,原图如图1所示.笔者认为此图有待商榷,不难看出编者想画一个由双量程的电流表、双量程的电压表和双倍率的欧姆表组成的多用电表,问题就出在双倍率的欧姆表上.让我们先回顾一下欧姆表的测量原理(图2):由闭合电路 PEP 3-1 Physics Education Elective (revised edition) Chapter 2 Section 8 Circuit diagram of a multi-meter, the original picture shown in Figure 1. I believe this figure is open to question, it is not difficult to see that the editor wants to draw a Multi-meter ammeter, dual-range voltmeter and double-ohmmeter multimeter, the problem lies in the double-rate ohmmeter. Let us first review the ohmmeter measurement principle (Figure 2): by the closed circuit