题目内容
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114109509672.gif)
如图11所示,在真空区域内,有宽度为L的匀强磁场,磁感应强度为B,磁场方向垂直纸面向里,MN、PQ是磁场的边界。质量为m,带电量为-q的粒子,先后两次沿着与MN夹角为θ(0<θ<90º)的方向垂直磁感线射入匀强磁场B中,第一次,粒子是经电压U1加速后射入磁场,粒子刚好没能从PQ边界射出磁场。第二次粒子是经电压U2加速后射入磁场,粒子则刚好垂直PQ射出磁场。不计重力的影响,粒子加速前速度认为是零,求:
小题1:为使粒子经电压U2加速射入磁场后沿直线运动,直至射出PQ边界,可在磁场区域加一匀强电场,求该电场的场强大小和方向。
小题2:加速电压
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114109540250.gif)
小题1:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114109540603.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114109556454.gif)
小题2:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114109571843.gif)
小题1: (1)如图答1所示,经电压
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114109587222.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114109602205.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114109634220.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082411410964919223.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114109665391.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114109680521.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114109680591.gif)
加匀强电场后,粒子在磁场中沿直线运动射出PQ边界的条件为Eq=Bq
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114109602205.gif)
由此可得出
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114109540603.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114109556454.gif)
小题2:
经电压
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114109743217.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114109758218.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114109774703.gif)
又
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114109790517.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114109805691.gif)
由于
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114109821540.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114109837546.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114109571843.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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