题目内容
把一线框从一匀强磁场中拉出,如图所示。第一次拉出的速率是 v ,第二次拉出速率是 2 v ,其它条件不变,则前后两次拉力大小之比是 ,拉力功率之比是 ,线框产生的热量之比是 ,通过导线截面的电量之比是 。![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152215351454.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152215351454.gif)
1:2 1:4 1:2 1:1
试题分析:线框被匀速拉出,拉力与安培力相等即
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152215367846.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152215413683.png)
拉力的功率为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152215647855.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152215959555.png)
线框产生的热量
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241522160221518.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152216147603.png)
通过导线截面的电量
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152216365986.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152216459513.png)
点评:电磁感应问题,有时从能量角度思考解决显得比较简单。克服安培力做功,就有电能产生,如果安培力做功,就有电能转化为其他形式的能。
![](http://thumb2018.1010pic.com/images/loading.gif)
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