题目内容
在如图所示的电路中,R1为定值电阻,R2为可变电阻,E为电源电动势,r为电源内阻(r< R1, r< R2).则以下说法中正确的是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250039506241537.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250039506241537.png)
A.当R2=R1+r时,R2上获得最大功率 |
B.当R1=R2+r时,R1上获得最大功率 |
C.当R2=0时,电源的输出功率最大 |
D.当R2=0时,电源的效率最大 |
AC
试题分析:根据电源的内电阻和外电阻相等的时候,电源的输出功率最大可知,当把
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003950639327.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003950655429.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003950671535.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003950686361.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003950702509.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003950639327.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003950733453.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003950749731.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003950686361.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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