题目内容
(18分)如图所示,平行且足够长的两条光滑金属导轨,相距0.5 m,与水平面夹角为30°,不计电阻,广阔的匀强磁场垂直穿过导轨平面,磁感应强度B=0.4 T,垂直导轨放置两金属棒
和
,长度均为0.5 m,电阻均为0.1Ω,质量分别为0.1 kg和0.2 kg,两金属棒与金属导轨接触良好且可沿导轨自由滑动。现
棒在外力作用下,以恒定速度ν=1.5m/s沿着导轨向上滑动,
棒则由静止释放。试求:(取g="10" m/s2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241420091283970.jpg)
(1)金属棒
产生的感应电动势;
(2)闭合回路中的最小电流和最大电流;
(3)金属棒
的最终速度。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142008380370.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142008473367.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142008380370.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142008473367.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241420091283970.jpg)
(1)金属棒
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142008380370.png)
(2)闭合回路中的最小电流和最大电流;
(3)金属棒
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142008473367.png)
(1)
(2)
(3)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142009752712.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142009269466.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142009394661.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241420095961160.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142009752712.png)
(18分)
(1)
---------------------------(3分)
(2)刚释放
棒时,
---------------------------(2分)
棒受到安培力为:
-------------------(1分)
棒受到的重力为:
---------------------------(1分)
棒沿导轨向下加速运动,即
闭合回路的
增大;电流也将增大,所以最小电流为:
---------------------------(4分)
当
棒的速度达到最大时,同路的电流最大,此时
棒的加速度为零。
由
得:
---------------------------(4分)
(3)由
得:
---------------------------(3分)
本题考查的是电磁感应定律和力学综合的问题,首先根据电磁感应定律计算出感应电动势;然后根据安培力的计算和力学规律计算出最大最小电流;最后根据欧姆定律计算出电压;
(1)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241420098151098.png)
(2)刚释放
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142008473367.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241420100491064.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142008473367.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241420102361039.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142008473367.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142010454980.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142010532700.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142010657506.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142010969644.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142009394661.png)
当
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142008473367.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142008473367.png)
由
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142011702815.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241420095961160.png)
(3)由
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241420119361025.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142009752712.png)
本题考查的是电磁感应定律和力学综合的问题,首先根据电磁感应定律计算出感应电动势;然后根据安培力的计算和力学规律计算出最大最小电流;最后根据欧姆定律计算出电压;
![](http://thumb2018.1010pic.com/images/loading.gif)
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