题目内容
如图所示,电源电动势为E,内阻为r。当开关S闭合,滑动变阻器的滑片P位于中点位置时,三个小灯泡
都正常发光,且亮度相同,则()
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241141150473510.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114115016413.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241141150473510.jpg)
A.三个灯泡的额定功率相同 |
B.三个灯泡的额定电压相同 |
C.三个灯泡的电阻按从大到小排列是![]() |
D.当滑片P稍微向左滑动,灯![]() ![]() ![]() |
AC
等效电路为
与变阻器R并联,再与
串联,再与
一起并联在电源两端。从题意知三个小灯泡正常发光且亮度相同,得额定功率相等。由于
上的电压最大,由
得
的电阻最大。又由于通过
的电流大于
的电流,由
得
的电阻大于
的电阻。当变阻器电阻变大时,总电阻变大,总电流变小,电源两端电压变大,
变亮。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114115297216.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114115297213.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114115094211.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114115094211.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114115375334.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114115094211.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114115297213.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114115297216.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114115453289.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114115297216.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114115297213.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114115094211.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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