【简答题】![](https://cos-cdn.shuashuati.com/shuashuati-web/2024-0521-0905-00/logo-new-ad743.png)
(9分)在“把电流表改装为电压表”的实验中,需要利用如图所示的电路测定电流表的内阻,步骤如下:
①接通S 1(S 2未接通),调节R 1,使电流表指针偏转到满刻度; ②再接通S 2,调节R 2,使电流表指针偏转到满刻度的1/3; ③读出R 2的阻值,可得到r g = (填表达式)已知电源的电动势为3V,内阻不计;电流表满偏电流为500μA ,其内阻约在100Ω左右。实验室配有的可变电阻有: A.电阻箱(0~999.9Ω) B.滑动变阻器(0~200Ω) C.滑动变阻器(0~10KΩ) D.滑动变阻器(0~100KΩ) ⑴电路中R 1应选 ,R 2应选 。(填序号) ⑵上述实验中电流表内阻的测量值和真实值相比 (选填“偏大”或“偏小”) ⑶如果测得该电流表阻值为100Ω,要将其改装为量程为3V电压表,应 联一个阻值为 Ω的电阻。
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