题目内容
正方形金属线框abcd,每边长![](http://thumb.1010pic.com/pic1/gzwl/wltk/ewebeditor/UploadFile080201/200881702052624.gif)
![](http://thumb.1010pic.com/pic1/gzwl/wltk/ewebeditor/UploadFile080201/200881702052707.gif)
![](http://thumb.1010pic.com/pic1/gzwl/wltk/ewebeditor/UploadFile080201/200881702052698.gif)
![](http://thumb.1010pic.com/pic1/gzwl/wltk/ewebeditor/UploadFile080201/200881702052150.gif)
(1)线框匀速上升的速度多大?此时磁场对线框的作用力多大?
(2)线框匀速上升过程中,重物M做功多少?其中有多少转变为电能?
![](http://thumb.1010pic.com/pic1/gzwl/wltk/ewebeditor/UploadFile080201/200881702052862.jpg)
解:(1)当线框上边
进入磁场,线圈中产生感应电流
, 由楞次定律可知产生阻碍运动的安培力为
由于线框匀速运动,线框受力平衡,
联立求解,得I = 8 A 由欧姆定律可得,E=IR=0 .16 V 由公式
,可求出
3 .2 m/s
0 .4 N (2)重物M 下降做的功为
0.14 J 由能量守恒可得产生的电能为E电
0 .04 J
![](http://thumb.1010pic.com/pic1/gzwl/wltk/ewebeditor/UploadFile080201/200881702052596.gif)
![](http://thumb.1010pic.com/pic1/gzwl/wltk/ewebeditor/UploadFile080201/200881702052309.gif)
![](http://thumb.1010pic.com/pic1/gzwl/wltk/ewebeditor/UploadFile080201/200881702052187.gif)
![](http://thumb.1010pic.com/pic1/gzwl/wltk/ewebeditor/UploadFile080201/200881702052132.gif)
![](http://thumb.1010pic.com/pic1/gzwl/wltk/ewebeditor/UploadFile080201/200881702052285.gif)
![](http://thumb.1010pic.com/pic1/gzwl/wltk/ewebeditor/UploadFile080201/200881702052847.gif)
![](http://thumb.1010pic.com/pic1/gzwl/wltk/ewebeditor/UploadFile080201/200881702052811.gif)
![](http://thumb.1010pic.com/pic1/gzwl/wltk/ewebeditor/UploadFile080201/200881702052982.gif)
![](http://thumb.1010pic.com/pic1/gzwl/wltk/ewebeditor/UploadFile080201/200881702052403.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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