题目内容
调整如图所示电路的可变电阻R的阻值,使电压表V的示数增大△U,在这个过程中( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082413072347614815.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082413072347614815.png)
A.通过R1的电流增加,增加量一定等于![]() |
B.R2两端电压减小,减少量一定等于![]() |
C.通过R2的电流减小,但减少量一定等于:![]() |
D.路端电压增加,增加量一定等于![]() |
A
当外电阻增大时根据闭合电路欧姆定律可知电路中电流减小,则内电压减小、R2两端电压减小、路端电压增大(电动势减去内电压)
定值电阻
所以通过R1的电流增加,增加量一定等于
A对
路端电压等于
两端电压之和,R2两端电压减小,减少量小于
(则必然通过R2的电流减小,但减少量小于:
)路端电压增加,增加量也小于
故可知BCD都错。
定值电阻
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130723757660.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130723586552.png)
路端电压等于
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130723882448.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130723632422.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130723664585.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130723632422.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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