把电流表改装成伏特表,是中学物理实验中的一个基本实验。这个实验的关键是测出电流表的内阻r_g。在80年版的高中物理课本(下册)中,是根据图1所示的电路来测电流表内阻的,其中电源为蓄电池,电动势为ε,内阻r;R为电阻箱;k为开关;G为待测电流表,满偏电流为I_g,内阻为r_g。测量时,先调电阻箱,使电流表的指针偏转到满刻度。记下电阻箱的示值R。根据欧姆定律 Converting an ammeter to a voltmeter is a basic experiment in high school physics experiments. The key to this experiment is to measure the ammeter’s internal resistance r_g. In the 80-year version of the high school physics textbook (second), is based on the circuit shown in Figure 1 to measure the ammeter resistance, where the power supply for the battery, electromotive force ε, internal resistance r; R for the resistance box; k for the switch; G is the ammeter to be measured, the full partial current is I_g, the internal resistance is r_g. Measurement, the first resistance box adjusted so that the ammeter pointer deflection to full scale. Note the resistance box R value. According to Ohm’s law