题目内容
一个交流发电机的示意图如图示,线圈匝数为N,单匝线圈面积为S,磁感应强度为B,在匀强磁场中以一定的角速度匀速转动,线圈总电阻为r,负载电阻为R,当开关K断开时,交流
电
压表示数为U,求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241245050108890.jpg)
(1)ab间电压的最大值是多少?
(2)当开关K闭合后,交流电压表的示数是多少?
(3)求线圈从中性面开始转过90°角的过程中,通过线圈导线截面的电量。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412450493265.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412450494765.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241245050108890.jpg)
(1)ab间电压的最大值是多少?
(2)当开关K闭合后,交流电压表的示数是多少?
(3)求线圈从中性面开始转过90°角的过程中,通过线圈导线截面的电量。
解:
(1)K断开时,电动势有效值即为U,ab间电压的最大值即为电动势的最大值
=![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124505025262.gif)
(2)K闭合后,交流电压表的示数![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124505041517.gif)
(3)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412450505673.gif)
,
=
故![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124505431759.gif)
(1)K断开时,电动势有效值即为U,ab间电压的最大值即为电动势的最大值
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124505010334.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124505025262.gif)
(2)K闭合后,交流电压表的示数
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124505041517.gif)
(3)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412450505673.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124505072673.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124505384262.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124505400436.gif)
故
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124505431759.gif)
略
![](http://thumb2018.1010pic.com/images/loading.gif)
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