题目内容
如图所示的电路中,闭合开关
,灯
、
正常发光.由于电路出现故障,突然发现灯
变亮,灯
变暗,电流表的示数变小,根据分析,发生的故障可能是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241142289294437.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114228851203.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114228866210.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114228882211.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114228866210.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114228882211.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241142289294437.gif)
A.![]() | B.![]() |
C.![]() | D.![]() |
A
画出原电路的等效电路图如图所示.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241142290074940.gif)
若
断路,图
增大,根据闭合电路欧姆定律
,得
减小,则
分得的电流变小,即
变暗,电流表的示数变小,又由
可知,可得路端电压增大,而
,
减小,可推得
增大,故
变亮.选项
正确.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241142290074940.gif)
若
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114228960218.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114229038226.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114229053457.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114229069214.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114228882211.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114228882211.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114229116408.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114229116467.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114229131340.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114229147234.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114228866210.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114229178200.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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