题目内容
如图所示,在平行板电容器正中有一个带电微粒。K闭合时,该微粒恰好能保持静止。在充电后将K断开,用什么方法能使该带电微粒向上运动打到上极板?( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241601051212343.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241601051212343.jpg)
A.上移上极板M | B.上移下极板N |
C.左移上极板M | D.把下极板N接地 |
C
试题分析:要使带电微粒向上运动,则粒子受到的电场力增大,因为电容器两端和电源断开,所以电容器两极板上的电荷量不变,根据公式
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160105168820.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160105262576.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241601054331182.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160105168820.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160105262576.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160106042599.png)
点评:做此类型题目,需要知道当极板和电源相连,两极板间的电压不变,当极板和电源断开,两极板所带的电荷量不变,然后根据公式
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160105168820.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160105262576.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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