题目内容
如图所示为交流发电机示意图,匝数为
匝的矩形线圈,边长分别为
和
,内阻为
,在磁感应强度
的匀强磁场中绕
轴以
的角速度匀速转动,线圈和外部
的电阻
相接.求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241928213851883.png)
(1)
断开时,电压表示数;
(2)电键
合上时,电压表和电流表示数;
(3)通过电阻
的电流最大值是多少?电阻
上所消耗的电功率是多少?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192815052527.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192815411531.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192815816579.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192816627439.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192817236611.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192818047411.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192818905874.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192819451519.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192820293349.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241928213851883.png)
(1)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192822384365.png)
(2)电键
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192822384365.png)
(3)通过电阻
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192820293349.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192820293349.png)
(1)50 V(2)40 V. (3)80 W
试题分析:(1)感应电动势最大值Em=nBSω=100×0.5×0.1×0.2×50
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192825395408.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192825395408.png)
S断开时,电压表示数为电源电动势有效值E=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192827235635.png)
(2)电键S合上时,由全电路欧姆定律I=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241928278441027.png)
即电流表示数为 2 A,电压表示数为 40 V.
(3)通过R中电流的最大值 Im=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192825395408.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192825395408.png)
电阻R上所消耗的电功率 P="IU=2×40" W="80" W
点评:本题难度较小,当线圈与磁场方向平行时感应电动势最大,最大值为nBSω,掌握交流电有效值和峰值的关系,把本题转化为电路问题处理第二问比较方便
![](http://thumb2018.1010pic.com/images/loading.gif)
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