题目内容
如图12-8所示,用一块金属板折成横截面为“
”形的金属槽放置在磁感应强度为B的匀强磁场中,并以速度v1向右匀速运动,从槽口右侧射入的带电微粒的速度是v2,如果微粒进入槽后恰能做匀速圆周运动,则微粒做匀速圆周运动的轨道半径r和周期T分别为( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241209576331793.jpg)
图12-8
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120957540410.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241209576331793.jpg)
图12-8
A.![]() | B.![]() | C.![]() | D.![]() |
B
金属板折成“
”形的金属槽放在磁感应强度为B的匀强磁场中,并以速度v1向右匀速运动时,左板将切割磁感线,上、下两板间产生电势差,由右手定则可知上板为正,下板为负,
,微粒做匀速圆周运动,则重力等于电场力,方向相反,故有
向心力由洛伦兹力提供,所以
得
,周期
,故B项正确.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120957540410.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120957883646.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120957898625.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120957914557.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120957930646.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120957945594.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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