题目内容
(15分)图是说明示波器工作原理的示意图,已知两平行板间的距离为d、板长为l电子经电压为U1的电场加速后从两平行板间的中央处垂直进入偏转电场.设电子质量为me、电荷量为e.
(1)求经电场加速后电子速度v的大小.
(2)要使电子离开偏转电场时的偏转角度最大,两平行板间的电压U2应是多少?电子动能多大?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241301513521651.png)
(1)求经电场加速后电子速度v的大小.
(2)要使电子离开偏转电场时的偏转角度最大,两平行板间的电压U2应是多少?电子动能多大?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241301513521651.png)
(1)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130152693935.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130152288835.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130152662796.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130152693935.png)
(1)电子经电压为U1的电场加速,根据动能定理:
(3分)
则经电场加速后电子的速度
. (2分)
(2)电子离开偏转电场偏转角度最大时的偏转量为
, (1分)
电子受到偏转电场的电场力
,
, (1分)
电子沿偏转电场方向做初速度为零的匀加速直线运动,有
(1分)
,
,
可解得两平行板间电压
. (2分)
又:
(2分)
(1分)
(2分)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130152725820.png)
则经电场加速后电子的速度
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130152288835.png)
(2)电子离开偏转电场偏转角度最大时的偏转量为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130152771433.png)
电子受到偏转电场的电场力
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130152803532.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130152834656.png)
电子沿偏转电场方向做初速度为零的匀加速直线运动,有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130153021750.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130153068665.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130153099478.png)
可解得两平行板间电压
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130152662796.png)
又:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130153161793.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130153193596.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130152693935.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目