题目内容
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114331142520.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114331157199.gif)
(1)导线中感应电流的大小;
(2)磁场对方框作用力的大小随时间的变化率。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241143312204033.jpg)
(1)
(2)
。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114331235509.gif)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114331251634.gif)
(1)导线框的感应电动势为
①
②
导线框中的电流为
③
式中R是导线框的电阻,根据电阻率公
式有
④
联立①②③④式,将
代入得
⑤
(2)导线框所受磁场的作用力的大小为
⑥
它随时间的变化率为
⑦
由⑤⑦式得
。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114331282468.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114331282558.gif)
导线框中的电流为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114331313302.gif)
式中R是导线框的电阻,根据电阻率公
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082411433132965.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114331438482.gif)
联立①②③④式,将
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114331469467.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114331235509.gif)
(2)导线框所受磁场的作用力的大小为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114331563304.gif)
它随时间的变化率为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114331563597.gif)
由⑤⑦式得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114331251634.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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