题目内容
如图所示,两根平行放置的导电轨道,间距为L,倾角为θ,轨道间接有电动势为E(内阻不计)的电源,整个导轨处在一个竖直向上的匀强磁场中,电阻为R的金属杆ab与轨道垂直放于导电轨道上静止,轨道的摩擦和电阻不计,要使ab杆静止,磁感应强度应多大?(设金属杆的质量为m)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241459337653311.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241459337653311.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145933812979.png)
试题分析:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241459338746371.png)
以金属杆为研究对象受力分析,则:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145933937793.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145933983799.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241459340301121.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145933812979.png)
点评:本题难度较小,导体棒受力较小,使该题计算过程较少,重点考查学生对受力分析的掌握和安培力方向的判断
![](http://thumb2018.1010pic.com/images/loading.gif)
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