题目内容
如图所示的电路中,电阻
,
,电源的电动势E=12V,内电阻r=1Ω,理想电流表A的读数I=0.4A。求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250016278223232.jpg)
(1)电阻
的阻值
(2)电源的输出功率
(3)电源的效率
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001627791516.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001627791573.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250016278223232.jpg)
(1)电阻
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001627838371.png)
(2)电源的输出功率
(3)电源的效率
(1)30
(2)6.84W (3)95%
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001627854333.png)
试题分析:(1)电阻R2及R3上的电压为U2=U3=IR2=0.4×15V=6V,则电源内阻及R1上的电压之和为6V,电路的总电流为
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250016278691053.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250016279001085.png)
(2)电源的输出功率
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250016279161332.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250016279321602.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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