题目内容
(14分)如图所示,两足够长的光滑固定金属导轨水平放置,相距为
, 一理想电流表A与两导轨相连,匀强磁场方向与导轨平面垂直,且竖直向下。一质量为m、有效电阻为R的导体棒在距磁场左边界
处由静止开始在水平恒力
作用下向右运动。导体棒进入磁场后,流经理想电流表的电流逐渐减小,最终稳定为
。整个运动过程中,导体棒与导轨接触良好,且始终与导轨保持垂直,不计导轨的电阻。求:
(1)该磁场磁感应强度的大小B;
(2)电流稳定后,导体棒运动速度的大小
;
(3)流经电流表电流的最大值
。![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241219477048059.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121947408197.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121947423204.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121947439219.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121947626205.gif)
(1)该磁场磁感应强度的大小B;
(2)电流稳定后,导体棒运动速度的大小
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121947642200.gif)
(3)流经电流表电流的最大值
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121947689318.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241219477048059.jpg)
(1)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121947720368.gif)
(2)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121947907501.gif)
(3)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121947689318.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121947938698.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121947720368.gif)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121947907501.gif)
(3)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121947689318.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121947938698.gif)
(1)电流稳定时,导体棒作匀速运动,有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121947954338.gif)
磁感应强度的大小
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121947720368.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412194800172.gif)
(2)根据能量守恒定律,有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121948016459.gif)
棒运动速度的大小
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121947642200.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121948110354.gif)
(或写作:感应电动势
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121948125439.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121948141329.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121948313344.gif)
由题意知
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121948313293.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121947907501.gif)
(3)导体棒刚进入磁场时速度最大,设为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121948359204.gif)
根据动能定理 有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121948375558.gif)
感应电动势
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121948391455.gif)
电流的最大值
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121947689318.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121948422396.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121947689318.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241219485151059.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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