题目

为了测量量程为3V的电压表V的内阻（内阻约2000Ω），实验室可以提供的器材有：                        电流表A1，量程为0.6A，内阻约0.1Ω                                                                              电压表V2，量程为5V，内阻约3500Ω                                                                              变阻器R1阻值范围为0﹣9999Ω                                                                                       变阻箱R2阻值范围为0﹣99.9Ω                                                                                        滑动变阻器R3，最大阻值约为100Ω，额定电流1.5A                                                        电源E，电动势6V，内阻约0.5Ω                                                                                     单刀单掷开关K，导线若干．                                                                                                                        （1）请从上述器材中选择必要的器材，设计一个测量电压表V的内阻的实验电路，在图1方框中画出电路原理图  （    电路原理图中的元件要用题中相应的英文字母标注），要求测量尽量准确．                 （2）根据你所画的电路原理图在图2所给的实物图上画出连线．                                    （3）说明实验所要测量的量：                                                                           ．写出计算电压表V的内阻RV的计算公式为RV=                                                                                                                ．                                                                                                                                         答案：（1）（2）（3）电压表V的示数U、电压表V2的示数U2、电阻箱R1的读数r1，电压表的内阻为Rv=

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