(一) 在高中物理课本下册第342页。学生实验把电流表改装成伏特表一节,其中把改装成的伏特表跟标准的伏特表进行核对的实验。教材安排的实验电路如图1所示。V是标准伏特表,改变变阻器R_2的阻值,使V的读数分别为0.5伏特、1伏特、1.5伏特时,观察改装的伏特表的读数。在实际的实验中,由于一般都没有 (a) In the textbook for high school physics, volume 342. The student experiment modified the ammeter into a voltmeter section, in which the converted voltmeter was checked against a standard voltmeter. The experimental circuit for the arrangement of teaching materials is shown in Figure 1. V is a standard voltmeter, changing the resistance of the varistor R_2 so that the V readings are 0.5 volts, 1 volts, and 1.5 volts, respectively, to observe the readings of the modified voltmeter. In the actual experiment, because there is generally no