题目内容
如图所示,电子在电势差为U1的加速电场中由静止开始运动,然后射入电势差为U2的两平行极板间的电场中,射入方向与极板平行,整个装置处在真空中,重力可忽略,在满足电子能射出平行板区的条件下,下述四种情况中,一定能使电子的偏转角
变大的是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241503599641740.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150359761297.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241503599641740.png)
A.U1变大,U2变大 | B.U1变大,U2变小 |
C.U1变小,U2变大 | D.U1变小,U2变小 |
C
试题分析:根据题意
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150400089814.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150400291826.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241504004471069.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241504005251135.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150359761297.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150400728349.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150400791377.png)
故选C
点评:中等难度。粒子的侧向位移、偏转角与粒子的q、m无关,仅取决于加速电场和偏转电场.即不同的带同种电性的粒子以同一位移、同一偏角射出电场
![](http://thumb2018.1010pic.com/images/loading.gif)
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