题目内容
如右图所示,电视机的显像管中,电子束的偏转是用磁偏转技术实现的。电子束经过加速电场后,进入一圆形匀强磁场区,磁场方向垂直于圆面。不加磁场时,电子束将通过磁场中心O点而打到屏幕上的中心M,加磁场后电子束偏转到P点外侧,现要使电子束偏转回到P点,可行的办法是 ( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250038179444652.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250038179444652.jpg)
A.减小加速电压 |
B.增加偏转磁场的磁感应强度 |
C.将圆形磁场区域向屏幕靠近些 |
D.将圆形磁场的半径增大些 |
C
试题分析:电子在加速电场中:根据动能定理得qU=
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003817944586.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003817975721.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003817991690.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003818006536.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003818022550.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003818038834.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003818053582.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003818069788.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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