题目内容
直流电路如图所示,在滑动变阻器的滑片P向右移动时,电源的( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250036170591800.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250036170591800.png)
A.总功率一定减小 |
B.效率一定增大 |
C.内部损耗功率一定减小 |
D.输出功率一定先增大后减小 |
ABC
试题分析:如图所示电路中,电流表测量干路电流,电压表测量路端电压,当滑动变阻器的滑动片P向右移动时,变阻器的电阻增大,根据闭合电路欧姆定律
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003617075616.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003617091549.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003617106441.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003617122758.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003617153563.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250036171691509.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003617184384.png)
故本题选择ABC。
本题是电路中动态变化分析问题,在认识电路结构的基础上,先分析局部电阻的变化.局部电阻增大,整个电路的电阻增大,再由闭合电路欧姆定律分析总电流和路端电压的变化。
![](http://thumb2018.1010pic.com/images/loading.gif)
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