题目内容
如图所示匀强电场分布在宽度为L的区域内,一个正离子以初速度
垂直于电场方向射入场强为E的匀强电场中,穿出电场区域时偏转角为
。在同样的宽度范围内,若改用方向垂直于纸面向里的匀强磁场,使该离子穿过磁场区域时偏转角也为
,求:(离子重力忽略不计)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241153347693427.jpg)
(1)正离子的电荷量q与其质量m的比值;
(2)匀强磁场磁感应强度B的大小;
(3)离子穿过匀强电场与穿过匀强磁场所用时间之比。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115334707205.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115334722200.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115334722200.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241153347693427.jpg)
(1)正离子的电荷量q与其质量m的比值;
(2)匀强磁场磁感应强度B的大小;
(3)离子穿过匀强电场与穿过匀强磁场所用时间之比。
(1)
(2)
(3)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115334816735.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115334785639.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115334800553.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115334816735.gif)
(1)(8分)正离子在电场中,水平方向做匀速直线运动,在电场中运动时间为t
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241153348313989.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241153348474497.jpg)
2分
离子在竖直方向做初速为零的匀加速直线运动射出电场时的速度为v
2分
如图所示
2分
① 2分
(2)(6分)磁场中,如图所示
② 2分
2分
③
①②③式联立
2分
(3)(4分)离子穿过电场的时间为
1分
离子穿过磁场的时间为
1分
2分
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241153348313989.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241153348474497.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115334863293.gif)
离子在竖直方向做初速为零的匀加速直线运动射出电场时的速度为v
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115334878584.gif)
如图所示
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115334894803.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115334785639.gif)
(2)(6分)磁场中,如图所示
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115334925382.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115334941594.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115334956750.gif)
①②③式联立
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115334800553.gif)
(3)(4分)离子穿过电场的时间为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115334987307.gif)
离子穿过磁场的时间为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115335003473.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115334816735.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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