题目内容
如图所示为一离子选择器,极板A、B间距为d,用来研究粒子的种类及偏向角,在A、B间加电压,B板电势高于A板电势,且A、B极板间有垂直纸面向外的匀强磁场,磁感应强度为Bl,P为一剐性内壁光滑绝缘的两端开口的直细管'右端开口在一半径为R的圆形磁场区域中心O点(即坐标原点),此磁场方向为垂直纸面向里的匀强磁场,磁感应强度为B2。细管的中心轴所在直线通过S粒子源,粒子源可发出电荷量为q、质量为m、速度大小、方向都不同粒子。当有粒子从圆形区域磁场射出时,其速度方向与x轴的夹角为偏向角。不计粒子重力。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250051006615048.jpg)
(1)若已知A、B间电压值为U,求能射入直细管中的粒子速度v的大小;
(2)若粒子能从圆形区域磁场射出时,其偏向角为
,求A、B间的电压值U1;
(3)若粒子能从圆形区域磁场射出时,A、B间的电压值U2应满足什么条件?
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250051006615048.jpg)
(1)若已知A、B间电压值为U,求能射入直细管中的粒子速度v的大小;
(2)若粒子能从圆形区域磁场射出时,其偏向角为
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005100676297.png)
(3)若粒子能从圆形区域磁场射出时,A、B间的电压值U2应满足什么条件?
(1)
(2)
(3)![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005100739999.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005100692567.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250051007071267.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005100739999.png)
试题分析:(1)射出磁场的速度即为射出选择器的速度,能射入P的管的粒子,速度满足:
则有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005100739619.png)
解得,
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005100754828.png)
(2)离子在
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005100785364.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005100801786.png)
如图,由几何关系得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/2014082500510081712018.jpg)
因
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005100832762.png)
联立①②③得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250051007071267.png)
(3)能射出
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005100785364.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005100879536.png)
联立①②⑤得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005100739999.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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