题目内容
(19分)如图所示的平行板器件中,存在相互垂直的匀强磁场和匀强电场,磁场的磁感应强度B1 =" 0.40" T,方向垂直纸面向里,电场强度E = 2.0×105 V/m,PQ为板间中线.紧靠平行板右侧边缘xOy坐标系的第一象限内,有垂直纸面的正三角形匀强磁场区域(图中未画出),磁感应强度B2 =" 0.25" T。一束带电量q = 8.0×10-19 C,质量m = 8.0×10-26 kg的正离子从P点射入平行板间,不计重力,沿中线PQ做直线运动,穿出平行板后从y轴上坐标为(0,0.2m)的Q点垂直y轴射向三角形磁场区,离子通过x轴时的速度方向与x轴正方向夹角为60°。则:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250044520944972.png)
(1)离子运动的速度为多大?
(2)若正三角形区域内的匀强磁场方向垂直纸面向外,离子在磁场中运动的时间是多少?
(3)若正三角形区域内的匀强磁场方向垂直纸面向里,正三角形磁场区域的最小边长为多少?
(4)第(3)问中离子出磁场后经多长时间到达X轴?
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250044520944972.png)
(1)离子运动的速度为多大?
(2)若正三角形区域内的匀强磁场方向垂直纸面向外,离子在磁场中运动的时间是多少?
(3)若正三角形区域内的匀强磁场方向垂直纸面向里,正三角形磁场区域的最小边长为多少?
(4)第(3)问中离子出磁场后经多长时间到达X轴?
(1)
;(2)
;(3)
(4)![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004452172653.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004452125725.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004452141716.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004452157553.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004452172653.png)
试题分析:(1)(2分)粒子在板间沿中线PQ做直线运动,说明受力平衡,由受力平衡条件得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004452203587.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004452219916.png)
(2)(5分)离子在匀强磁场中做匀速圆周运动,由牛顿第二定律得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004452281751.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004452297574.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250044523281006.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004452344985.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/2014082500445235918463.png)
规范做好示意图1分
(3)(8分)离子在匀强磁场中做匀速圆周运动,过程示意图如图所示,规范做图(2分)
由牛顿第二定律得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004452281751.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004452297574.png)
几何关系得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004452406937.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004452422297.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004452437578.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004452453164.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004452157553.png)
(4)(4分)离子出磁场后做匀速直线运动,几何关系得位移
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004452484970.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004452500451.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004452515606.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目