题目内容
如图所示,理想变压器的副线圈上接有三个灯泡,原线圈与一个灯泡串联接在交流电源上.若四个灯泡完全相同,且都正常发光,则电源两端的电压U1与灯泡两端的电压U2之比为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241235416614741.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241235416614741.jpg)
A.1∶1 | B.2∶1 | C.3∶1 | D.4∶1 |
D
灯泡都正常发光,所以通过每个灯泡的电流都相同,设原线圈电流为I。副线圈电流为3I,灯泡正常发光的电压为u
根据变压器原副线圈匝数与电流、电压的关系:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123541724804.png)
所以副线圈电压U2 =
=u
原线圈电压为
=3u
根据电路的串并联关系U1=
+u=4u
所以电源电压与灯泡两端电压之比为4:1,
故答案选D
根据变压器原副线圈匝数与电流、电压的关系:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123541724804.png)
所以副线圈电压U2 =
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123541755354.png)
原线圈电压为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123541771326.png)
根据电路的串并联关系U1=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123541771326.png)
所以电源电压与灯泡两端电压之比为4:1,
故答案选D
![](http://thumb2018.1010pic.com/images/loading.gif)
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