电流表、电压表示数变化通常是由于电路变化引起的，电表示数变化的根本原因是接入电路的滑动变阻器电阻变化。或电路中开关的通断导致某个（或某部分）电阻的变化，总之是电路的电阻发生了变化．下面通过例题来说明这类问题的分析方法．例ｌ如图１所示的电路中，当滑动变阻器 The change of the ammeter and voltage indicates that the change is usually caused by a circuit change. The fundamental reason for the change in the number of electrical representations is the change in the resistance of the sliding rheostat connected to the circuit. Or the on/off of the switch in the circuit leads to a change in the resistance of one (or part), in a word, the resistance of the circuit changes. The following examples illustrate the analysis of this type of problem. Example 1 in the circuit shown in Figure 1, when the sliding rheostat