题目内容
如图所示,将硬导线中间一段折成不封闭的正方形,每条边长均为
,它在磁感应强度为
、方向垂直纸面向外的匀强磁场中绕垂直于磁场方向的
轴匀速转动,角速度为
,导线在
两处通过电刷与外电路连接。设外电路电阻为
,其余电阻忽略不计,则整个回路的功率为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241543312624628.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154330544280.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154330638309.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154330762370.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154330887308.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154331059398.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154331121303.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241543312624628.jpg)
A.![]() | B.![]() |
C.![]() | D.![]() |
C
试题分析:根据Em=nBSω可以求得最大电动势的大小,由
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154331761519.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154331886651.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154331948618.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154332135896.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154331761519.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154332400804.png)
故选C.
点评:掌握住最大感应电动势的计算方法是本题的关键,记住最大感应电动势Em=nBSω和有效值之间的关系,计算时的电压要用有效值来计算.
![](http://thumb2018.1010pic.com/images/loading.gif)
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