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题目实验室里可以用欧姆表来直接测量电阻,图1虚线框内是欧姆表的简化结构图,它由灵敏电流表、电源、变阻器等组成,在a、b间接入一个电阻R,电路中就有一个对应的电流I,即电阻R与电流表的读数I具有一一对应关系。所以,由电流表的指针位置就可以知道电阻R大小,为了方便,事先在电流表的刻度盘上标出了电阻的欧姆值。欧姆表在测量电阻前都需要调零,即把a,b两接
The ohmmeter can be used to directly measure the resistance in the laboratory. The dashed box in Figure 1 is a simplified structure diagram of an ohmmeter. It consists of a sensitive ammeter, a power supply, a rheostat, etc. A resistor R is connected between a and b. There is a corresponding current I, that is, the resistance R has a one-to-one correspondence with the reading I of the ammeter. Therefore, the magnitude of the resistance R can be known from the pointer position of the ammeter. For convenience, the ohmic value of the resistance is marked on the scale of the ammeter in advance. The ohmmeter needs to be zero before measuring the resistance, that is to connect a and b