题目内容
(19分)
如图所示,电源电动势
内阻
,电阻
。间距
的两平行金属板水平放置,板间分布有垂直于纸面向里、磁感应强度
的匀强磁场。闭合开关
,板间电场视为匀强电场,将一带正电的小球以初速度
沿两板间中线水平射入板间。设滑动变阻器接入电路的阻值为
,忽略空气对小球的作用,取
。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241217077105069.jpg)
(1)当
时,电阻
消耗的电功率是多大?
(2)若小球进入板间做匀速度圆周运动并与板相碰,碰时速度与初速度的夹角为
,则RX是多少?
如图所示,电源电动势
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707461424.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707570290.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707601618.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707617419.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707632266.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707648203.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707663445.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707679218.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707695477.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241217077105069.jpg)
(1)当
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707726343.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707741220.gif)
(2)若小球进入板间做匀速度圆周运动并与板相碰,碰时速度与初速度的夹角为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707757245.gif)
(1)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707866444.gif)
(2)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707882433.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707866444.gif)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707882433.gif)
本题主要考查电路分析,含容电路分析,及带电粒子在复合场中的运动的综合运用的问题。对考生分析问题和建立正确的物理模型能力的考查。
(1)设
和
的并联电阻为
,有:
①
两端的电压为:
②
消耗的电功率为:
③
当
时,联立①②③式,代入数据,解得:
④
(2)设小球质量为m,电荷量为q,小球做匀速圆周运动时,有:
⑤
⑥
设小球做圆周运动的半径为r,有:
⑦
由几何关系有:
⑧
联立①②⑤⑥⑦⑧式,代人数据,解得:
⑨
(1)设
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707679218.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707741220.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707944204.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707991463.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707741220.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121708022601.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707741220.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121708100348.gif)
当
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121708256453.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707866444.gif)
(2)设小球质量为m,电荷量为q,小球做匀速圆周运动时,有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121708303428.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121708319413.gif)
设小球做圆周运动的半径为r,有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121708334517.gif)
由几何关系有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121708350346.gif)
联立①②⑤⑥⑦⑧式,代人数据,解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121707882433.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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