题目内容
待测电阻Rx的阻值约为20Ω,现要测量其阻值,实验室提供器材如下:
E.滑动变阻器R1,最大阻值为5Ω,额定电流为1.0A
F.滑动变阻器R2,最大阻值为5Ω,额定电流为0.5A
G.电源E,电动势E=4V(内阻不计)
H.电键S及导线若干
(1)为了使电表调节范围较大,测量准确,测量时电表读数不得小于其量程的
,请从所给的器材中选择合适的实验器材 _______________________(均用器材前对应的序号字母填写);
(2)根据你选择的实验器材,请你在虚线框内画出测量Rx的最佳实验电路图并标明元件符号;
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152808848611.png)
(3)待测电阻的表达式为Rx=________________,式中各符号的物理意义为________________
______________________________________________________________________________________。
A.电流表A1(量程150mA,内阻约为10Ω) |
B.电流表A2(量程20mA,内阻r2=30Ω) |
C.电压表V(量程15V,内阻约为3000Ω) |
D.定值电阻R0=100Ω |
F.滑动变阻器R2,最大阻值为5Ω,额定电流为0.5A
G.电源E,电动势E=4V(内阻不计)
H.电键S及导线若干
(1)为了使电表调节范围较大,测量准确,测量时电表读数不得小于其量程的
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152808770327.png)
(2)根据你选择的实验器材,请你在虚线框内画出测量Rx的最佳实验电路图并标明元件符号;
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152808848611.png)
(3)待测电阻的表达式为Rx=________________,式中各符号的物理意义为________________
______________________________________________________________________________________。
(1)ABDEGH
(2)实验电路图如下
(3)
,其中
、
分别为
和
表示数,
与
分别为定值电阻和
内阻的阻值。
(2)实验电路图如下
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241528089103035.png)
(3)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152808972768.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152809066293.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152809128324.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152809206328.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152809284354.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152809347356.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152809409321.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152809284354.png)
试题分析:(1)电源电动势为4V,电压表量程15V太大不能用,须将小量程的电流表与分压电阻串联,可改装成电压表,电流表需要知道两个参数:量程和内阻,故电流表选
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152809550367.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152809347356.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152809971342.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152810049752.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152810111327.png)
(2)将
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152809550367.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152810532855.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152810610694.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152809971342.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241528089103035.png)
(3)由欧姆定律可得待测电阻
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241528108291096.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152809066293.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152809128324.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152809971342.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152809550367.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152809347356.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152809409321.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152809550367.png)
点评:本题是电表改装与伏安法测量电阻两个实验的组合,考查灵活选择器材和实验方法的能力。
![](http://thumb2018.1010pic.com/images/loading.gif)
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