题目内容
某同学将一直流电源的总功率PE、输出功率PR和电源内部的发热功率Pr随电流I变化的图线画在同一坐标系内,如图,根据图线可知下列说法正确的是
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250037424705331.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250037424705331.jpg)
A.反映Pr变化的图线是b |
B.电源电动势约为8V |
C.当外电阻约为2Ω时,输出功率最大 |
D.当电流为0.5A时,外电路的电阻约为6Ω。 |
CD
试题分析:直流电源的总功率
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003742501522.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250037425161002.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003742516516.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003742532654.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003742548612.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003742563496.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003742579498.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003742594423.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250037426101102.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003742626492.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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