题目内容
(16分) 如图所示,光滑导轨与水平面成θ角,导轨宽L。匀强磁场磁感应强度为B。金属杆长也为L,质量为m,水平放在导轨上。当回路总电流为I1时,金属杆正好能静止。求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250024209872027.jpg)
⑴B至少多大?这时B的方向如何?
⑵若保持B的大小不变而将B的方向改为竖直向上,应把回路总电流I2调到多大才能使金属杆保持静止?
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250024209872027.jpg)
⑴B至少多大?这时B的方向如何?
⑵若保持B的大小不变而将B的方向改为竖直向上,应把回路总电流I2调到多大才能使金属杆保持静止?
(1)
,垂直于导轨平面向上;(2)![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002421018666.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002421003874.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002421018666.png)
试题分析:(1)只有当安培力方向沿导轨平面向上时,安培力才最小,B才会可能最小,根据左手定则,这时B应垂直于导轨平面向上,由题意得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002421049789.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002421003874.png)
(2)当B的方向改为竖直向上时,这时安培力的方向变为水平向右,由题意得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002421081913.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002421018666.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目