题目内容
带电粒子(不计重力)以初速度v0从a点进入匀强磁场,如图。运动中经过b点,oa=ob。若撤去磁场加一个与y轴平行的匀强电场,仍以v0从a点进入电场,粒子仍能通过b点,那么电场强度E与磁感强度B之比E/B为:( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241307458311930.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241307458311930.png)
A.v0 | B.1 | C.2v0 | D.![]() |
C
带电粒子在磁场中的转动半径
,换成与y轴平行的匀强电场则带电粒子做类平抛运动,可得竖直方向
水平方向
,加速度
联立可解得E/B=2v0选C
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130745987709.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130746034622.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130746065485.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130746128651.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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