欧姆表是根据闭合电路欧姆定律制成的. 它的原理如图1所示,G是电流表,内阻为Rg, 满偏电流为Ig;电池的电动势为ε,内阻为r;R 为调零电阻．当黑、红表笔短接时(图甲)．相当于被测电阻Rx=0,调节R的阻值,使电流表满偏,即 Ig=ε/Rg+r+R=ε/R内,R内为欧姆表内阻·则指针 The ohmmeter is made according to the closed circuit Ohm’s law. Its principle is shown in Figure 1. G is the ammeter, the internal resistance is Rg, the full bias current is Ig; the electromotive force of the battery is ε, the internal resistance is r; R is the adjustment Zero resistance. When black and red pens are short-circuited (Figure A). Corresponds to the measured resistance Rx = 0, adjust the resistance of R, so that the ammeter is full, that is, Ig = ε / Rg + r + R = ε / R, R within the resistance of the ohmmeter · then the pointer