题目内容
两个半径均为R的圆形平板电极,平行正对放置,相距为d,极板间的电势差为U,板间电场可以认为是均匀的。一个
粒子(42He)从正极板边缘以某一初速度垂直于电场方向射入两极板之间,到达负极板时恰好落在极板中心。已知质子电荷为e,质子和中子的质量均视为m,忽略重力和空气阻力的影响,求:
(1)极板间的电场强度E;
(2)
粒子在极板间运动的加速度a;
(3)
粒子的初速度v0。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150547510310.png)
(1)极板间的电场强度E;
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150547510310.png)
(3)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150547510310.png)
(1)
(2)
(3)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150547885848.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150547713464.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150547822683.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150547885848.png)
试题分析:(1)极间场强
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150548088593.png)
(2)粒子电荷为2e,质量为4m,所受电场为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150548322843.png)
粒子在极板间运动的加速度
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150548446969.png)
(3)由
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150548556671.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241505486651086.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241505488051091.png)
点评:中等难度。带电粒子在电场中偏转时做类平抛运动,即在垂直于电场方向电场力不做功,带电粒子做匀速直线运动,而沿电场方向电场力做正功,带电粒子做匀加速直线运动。因此要注意运动合成与分解的方法和电场力运动规律的灵活应用.
![](http://thumb2018.1010pic.com/images/loading.gif)
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