题目内容
如图是一个多量程多用电表的简化电路图,电流、电压和电阻的测量都各有两个量程(或分度值)不同的档位。1、2两个档位为电流表档位,其中的大量程是小量程的10倍。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082413093882252760.png)
小题1:关于此多用表,下列说法正确的是: ( )
小题2:已知表头G的满偏电流为100μA,内阻为990Ω,图中的电源E的电动势均为3.5V,当把转换开关S旋到位置4,在AB之间接3500Ω电阻时,表头G刚好半偏,该测量过程操作的顺序和步骤都正确无误,则R1= Ω,R2= Ω。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082413093882252760.png)
小题1:关于此多用表,下列说法正确的是: ( )
A.当转换开关S旋到位置4时,是电阻档 |
B.当转换开关S旋到位置6时,是电压档 |
C.当转换开关S旋到5的量程比旋到6的量程大 |
D.A表笔为红表笔,B表笔为黑表笔 |
小题1:ABD
小题2:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130938853345.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130938900333.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130939025381.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130938900333.png)
“该测量过程操作的顺序和步骤都正确无 误”,意味着之前已经将A、B短接调零了(即让表头满偏),在AB之间接3500
电阻时,表头G刚好半偏,说明:当表头半偏时,改装后的电流表的总内阻
,则转换开关S在2时(如图a),电流表的量程为![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241309393841234.png)
依题意, 转换开关S在1(如图b)时,电流表的量程为![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130939415630.png)
由表头G的满偏电流为
、内阻为990
和并联电路电流分配规律
可解得
11
--------3分
99
-------3分
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130938900333.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130939353704.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241309393841234.png)
依题意, 转换开关S在1(如图b)时,电流表的量程为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130939415630.png)
由表头G的满偏电流为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130939446506.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130938900333.png)
可解得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130938853345.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130938900333.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130939025381.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130938900333.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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