题目内容
如图所示,磁感应强度为B的匀强磁场有理想边界,用力将矩形线圈从有边界的磁场中匀速拉出,在其他条件不变的情况下( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241546412702872.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241546412702872.jpg)
A.速度越大,拉力做功越多 |
B.线圈边长L1越大,拉力做功越多 |
C.线圈边长L2越大,拉力做功越多 |
D.线圈电阻越大,拉力做功越多 |
ABC
试题分析:因为是匀速拉出的,所以受到的拉力等于安培力,即
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241546416601177.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241546418001101.png)
点评:做本题的关键是求出拉力做功的表达式,根据表达式分析,千万不能将两个边的作用弄反了
![](http://thumb2018.1010pic.com/images/loading.gif)
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