题目内容
如图所示,理想变压器的原副线圈的匝数比n1∶n2=2∶1,原线圈接正弦式交流电,副线圈接电动机,电动机线圈电阻为R,当输入端接通电源后,电流表读数为I,电动机带动一质量为m的重物以速度v匀速上升,若电动机因摩擦造成的能量损失不计,电压表、电流表均为理想电表,则图中电压表的读数为( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241421388294754.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241421388294754.jpg)
A.4IR+![]() | B.![]() |
C.4IR | D.![]() ![]() |
A
设电动机电路工作电流为
,由公式
得
,变压器两端电功率相等,即
,得电压表读数为
,A对;
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142139437318.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142139499631.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142139546456.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142139593815.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142139733759.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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