题目内容
如图所示a、b间接人正弦交流电,变压器右侧部分为一火灾报警系统原理图,R2为热敏电阻,随着温度升高其电阻变小,所有电表均为理想电表,电流表A2为值班室的显示器, 显示通过R1的电流,电压表V2显示加在报警器上的电压(报警器未画出),R3为一定值电阻。当R2所在处出现火情时,以下说法中正确的是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250040011546020.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250040011546020.jpg)
A.V1的示数不变,V2的示数减小 |
B.V1的示数减小,V2的示数减小 |
C.A 1的示数增大,A 2的示数增大 |
D.A 1的示数减小,A 2的示数减小 |
A
试题分析:理想变压器原副线圈电压表等于匝数比,原线圈电压决定副线圈电压,在匝数比没有变化和输入电压不变情况下,原线圈电压
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004001169349.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004001185344.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004001201361.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250040012161005.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004001232495.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004001247385.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004001263702.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004001279332.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004001294365.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004001310407.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004001325373.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004001341327.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004001372354.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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