题目内容
如图所示,理想变压器原、副线圈的匝数之比是10:1,原线圈输入交变电压
(V),O是副线圈中心抽出的线头,
,则( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412372115815665.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123721096820.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123721112737.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412372115815665.png)
A.开关S断开时,电流表的示数为0.05A |
B.开关S闭合时,电流表的示数为0.05A |
C.开关S断开时,两电阻总的电功率为![]() |
D.开关S闭合时,两电阻总的电功率为![]() |
AD
分析:根据公式可以求得电压的有效值、周期和频率等,再根据电压与匝数成正比、电流与匝数成反比和欧姆定律逐项分析.
解答:解:A、由电压公式知输入电压的有效值为100V,再根据电压与匝数成正比知输出电压为10V.S断开时,副线圈中的电流为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123721205490.png)
B、S闭合时,两电阻并联,电压为5V,副线圈中电流为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123721236279.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123721283360.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123721314373.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123721346408.png)
C、开关S断开时,两电阻总的电功率为UI=10×0.5=5W故C错误;
D、S闭合时,两电阻总的电功率为UI=5×
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123721314373.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123721408458.png)
故选AD
点评:掌握住理想变压器的电压、电流之间的关系,最大值和有效值之间的关系结合欧姆定律即可解决本题.
![](http://thumb2018.1010pic.com/images/loading.gif)
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