题目内容
如图所示,电路中电源电动势E恒定,内阻r=2Ω,定值电阻R3=4Ω。ab段电路消耗的电功率在开关S断开与闭合时相等,则以下说法中正确的是
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241600172142471.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241600172142471.png)
A.电阻R1、R2可能分别为3Ω、9Ω |
B.电阻R1、R2可能分别为4Ω、6Ω |
C.开关S断开时电压表的示数一定等于S闭合时的示数 |
D.开关S断开与闭合时,电压表的示数变化量大小与电流表的示数变化量大小之比与R1、R2无关 |
AD
试题分析:AB、由题知,电键S断开与闭合时,ab段电路消耗的电功率相等,则有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241600173851807.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160017448533.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160017682538.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160017853519.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160018025554.png)
C、电键S断开时外电路总电阻大于S闭合时外电路总电阻,则电键S断开时电压表的示数一定大于S闭合时的示数;错误
D、根据闭合电路欧姆定律得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160018119783.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160018243959.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160018399327.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160018587361.png)
故选AD
点评:当S闭合时
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160018587361.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160018399327.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160018587361.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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