题目内容
如图所示,把一个线框从一匀强磁场中匀速拉出(线框原来全在磁场中)。第一次拉出的速率是v,第二次拉出速率是2v,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 ,拉力做功的绝对值之比 ,是安培力做功的绝对值之比是 ,线框产生的热量之比是 ,通过导线某一横截面的电量之比是 。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250020000452514.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250020000452514.png)
1:2 1:4 1:2 1:2 1:2 1:1
试题分析:根据安培力公式
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002000061503.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002000092512.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002000108500.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002000139731.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002000154515.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002000170783.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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