题目内容
如图所示,理想变压器原线圈接在交流电源上,副线圈向电阻R1、R2和R3供电, A为理想交流电流表,V为理想交流电压表,开关S闭合后与闭合前相比:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241557425554667.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241557425554667.jpg)
A.V示数变大,A示数变小,R1消耗的电功率变大 |
B.V示数变大,A示数变大,R1消耗的电功率大 |
C.V示数变小,A示数变小,R1消耗的电功率变小 |
D.V示数变小,A示数变大,R1消耗的电功率变小 |
D
试题分析:因为变压器两端的线圈的匝数不变,所以原副线圈的端电压不变,当闭合S后,副线圈中总电阻减小,所以总电流增大,故根据
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155742571643.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155742649365.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155742649365.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155743351606.png)
点评:做此类型的题目需要根据部分电路的变化推到整体变化,再由整体变化推导另外部分的变化
![](http://thumb2018.1010pic.com/images/loading.gif)
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