题目内容
如图所示,电子(质量m,电量e)经加速电场(电压为U1)后由中央进入偏转电场(电压为U2),然后从下极板的边缘飞出偏转电场,已知偏转电场极板长度为L,板间距离为d. 求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241239185806819.png)
(1)该电子在偏转电场运动的加速度大小;
(2) 电子飞出电场时的动能.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241239185806819.png)
(1)该电子在偏转电场运动的加速度大小;
(2) 电子飞出电场时的动能.
略
(1) 电子在加速电场中做变速直线运动,设在进入中央偏转电场的速度为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123918611325.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123918627283.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123918751878.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123918798814.png)
对电子在中央偏转电场中运动进行分解:
水平方向做匀速直线运动,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123918861465.png)
竖直方向做变速直线运动,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123918923724.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123918954460.png)
由
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123918861465.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123918923724.png)
电子在偏转电场运动的加速度大小
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241239190791648.png)
(2) 电子飞出电场时的速度为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123919095605.png)
竖直方向的末速度
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241239191261981.png)
所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241239191881850.png)
电子飞出电场时的动能为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241239192042998.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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