题目内容
如图甲所示,在一个正方形金属线圈区域内存在着磁感应强度B随时间变化的匀强磁场,磁场的方向与线圈平面垂直.金属线圈所围的面积S=200 cm2,匝数n=1 000,线圈电阻r=1.0 Ω.线圈与电阻R构成闭合回路,电阻的
阻值R =4.0 Ω.匀强磁场的磁感应强度随时间变化的情况如
图乙所示,求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241858067283491.jpg)
(1) 在t=2.0 s时通过电阻R的感应电流的大小;
(2) 在t=5.0 s时刻,线圈端点a、b间的电压;
阻值R =4.0 Ω.匀强磁场的磁感应强度随时间变化的情况如
图乙所示,求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241858067283491.jpg)
(1) 在t=2.0 s时通过电阻R的感应电流的大小;
(2) 在t=5.0 s时刻,线圈端点a、b间的电压;
(1)
(2)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824185806993818.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824185806759541.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824185806993818.png)
试题分析:(1) 根据法拉第电磁感应定律,0~4.0 s时间内线圈中磁通量均匀变化,产生恒定的感应电流.t1=2.0 s时的感应电动势
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241858072741283.png)
根据闭合电路欧姆定律,闭合回路中的感生电流
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824185807508649.png)
解得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824185806759541.png)
由图像可知,在4.0秒到6.0秒时间内,线圈的感应电动势
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824185807976934.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824185808210169.png)
根据闭合电路欧姆定律,5.0s时刻闭合回路中的感生电流
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824185808428664.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824185808693570.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824185806993818.png)
点评:本题是电磁感应与电路知识简单的综合.当穿过回路的磁通量均匀变化时,回路中产生恒定电流,
![](http://thumb2018.1010pic.com/images/loading.gif)
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