题目

某同学为了精确测量电阻Rx（阻值约为80Ω）的阻值，实验室提供了下列可选用的器材：                        A．电流表A（量程为50mA，内阻约为50Ω）                                                            B．电压表V1（量程为3V，内阻约为10kΩ）                                                              C．电压表V2（量程为15V，内阻约为20kΩ）                                                            D．滑动变阻器R1 （最大阻值为10Ω，额定电流1A）                                         E．滑动变阻器R2（阻值范围0～2kΩ，允许通过的最大电流0.5A）                            F．低压直流电源E （电动势4.5V，内阻较小）                                                   G．电键S，导线若干                                                                                                 （1）为提高实验结果的准确程度，电压表应选用                                         ，滑动变阻器应选用              ．（填器材代号） （2）为达到上述目的，请在虚线框内画出正确的实验电路原理图，并标明所用器材的代号．                                                                                                                                                                                                                                答案：V1，R1，（2）如图所示．

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