题目内容
如图所示,匀强磁场方向垂直于线圈平面,先后两次将线圈从同一位置匀速地拉出有界磁场,第一次拉出时速度为 v1=v0,第二次拉出时速度为 v2=2v0,前后两次拉出线圈的过程中,下列说法正确的是( )。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241616009222209.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241616009222209.jpg)
A.线圈中感应电流之比是1∶2 |
B.线圈中产生的热量之比是2∶1 |
C.沿运动方向作用在线框上的外力的功率之比为1∶2 |
D.流过任一横截面感应电荷量之比为1∶1 |
AD
试题分析:在拉出过程中,产生的感应电动势大小为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161600937530.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161601265585.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161601655553.png)
根据欧姆定律
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161601842521.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161601951542.png)
根据公式
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161602092570.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161602217613.png)
根据公式
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161602341489.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161602482462.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161602607555.png)
因为过程中磁通量变化量一样,所以流过任一横截面感应电荷量相同,D正确,
故选AD
点评:本题采用比例法,用相同的物理量表示所求量,再求比例,是常用的方法.常见问题.
![](http://thumb2018.1010pic.com/images/loading.gif)
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