题目内容
一平行板电容器C,极板是水平放置的,它与三个可变电阻及电源连接如图电路,有一个质量为m的带电油滴悬浮在电容器的两极板之间,静止不动.现要使油滴上升,可采用的办法是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241516443033348.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241516443033348.png)
A.增大R1 | B.增大R2 | C.增大R3 | D.减小R2 |
CD
试题分析:由图知R1的变化不影响电路的电流,即电容器两极板间的电压不变,油滴仍静止,A错;增大R2,电路的总电阻增大,由闭合电路的欧姆定律
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151644381647.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151644459545.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151644381647.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151644459545.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151644381647.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151644708635.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151644459545.png)
点评:本题要求学生明确动态分析的总体思路是先由局部阻值的变化得出总电阻的变化,再整体据闭合电路的欧姆定律得出电路中总电流的变化,再局部就是由串、并联电路的特点去分析。
![](http://thumb2018.1010pic.com/images/loading.gif)
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