题目内容
在如右图所示电路中,闭合开关S,当滑动变阻器的滑动触头P向下滑动时,四个理想电表的示数都发生变化,电表的示数分别用I、U1、U2和U3表示,电表示数变化量的大小分别用
、
、
和
表示。下列关于比值的说法,错误的是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241444211794245.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824144419869368.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824144419947437.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824144420040466.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824144420103468.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241444211794245.jpg)
A.![]() ![]() | B.![]() ![]() |
C.![]() ![]() | D.![]() ![]() |
B
本题考查闭合电路欧姆定律,
=
=R1,由于R1不变,故
不变,
不变.同理
=R2,由于R2变大,所以
变大.但是
=
=R1+r,所以
不变.而
=R2+R1,所以
变大,由于
=
=r,所以
不变.故选项A、C、D正确
点评:在闭合电路中各个用电器和电源内阻分得的电压总和保持不变,电阻R =
=
,根据电阻变化来判断
的变化也是一个方法
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824144421195435.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824144421881559.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824144421195435.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824144421241550.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824144421288462.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824144421288462.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824144421351584.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824144422505776.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824144421351584.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824144421507467.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824144421507467.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824144421616581.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824144423316539.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824144421616581.png)
点评:在闭合电路中各个用电器和电源内阻分得的电压总和保持不变,电阻R =
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824144423488406.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824144423737526.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824144423737526.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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