题目内容
如图,圆柱桶的一个横截面在xOy平面内,与x轴相切于坐标原点O,圆心为
,半径为
,在与y轴成
=
角的直径两端开有小孔
和
。现在桶内加匀强磁场,磁感应强度为
,方向平行于轴线向外,该装置就是一个离子速度选择器。离子束以某一入射角从
孔射入,
取值不同,就有不同速率的离子从
孔射出。x轴下方存在方向沿x轴正向的匀强电场,其右边界上放置一个与y轴平行、间距为
的挡板,板上开有小孔
(与
、
、
共线),紧靠
孔处安放一离子探测器。当离子源S以入射角
对准
孔发射某种正离子,电场场强大小为
时,探测器检测到有离子射入。不计离子重力和离子间的作用,打在桶壁和挡板上的离子不再反弹。试求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082419051393410368.jpg)
(1)射入探测器上的离子的比荷(电荷量与质量之比);
(2)射入探测器上的离子在磁场和电场中运动的时间之比。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190508428323.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190508833315.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190509176283.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190509504352.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190509769360.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190510066360.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190510502304.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190509769360.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190510502304.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190510066360.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190511345539.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190511672344.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190508428323.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190509769360.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190510066360.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190511672344.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190509176283.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190509769360.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190513669311.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082419051393410368.jpg)
(1)射入探测器上的离子的比荷(电荷量与质量之比);
(2)射入探测器上的离子在磁场和电场中运动的时间之比。
(1)
(2)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190514262746.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190513950798.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190514262746.png)
试题分析:(1)离子的比荷:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190513950798.png)
(2)离子在磁场和电场中运动的时间之比为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190514262746.png)
点评:带电粒子在匀强电场中运动时,要注意应用运动的合成和分解;而在磁场中运动时为匀速圆周运动,在解题时要注意应用好平抛和圆周运动的性质.
![](http://thumb2018.1010pic.com/images/loading.gif)
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