题目内容
在范围足够大,方向竖直向下的匀强磁场中,B=0.2 T,有一水平放置的光滑框架,宽度为L=0.4 m,如图所示,框架上放置一质量为0.05 kg,电阻为1 Ω的金属杆cd,框架电阻不计.若cd杆以恒定加速度a=2 m/s2,由静止开始做匀变速运动,则
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241754175292186.jpg)
(1)在5 s内平均感应电动势是多少?
(2)第5 s末,回路中的电流多大?
(3)第5 s末,作用在cd杆上的水平外力多大?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241754175292186.jpg)
(1)在5 s内平均感应电动势是多少?
(2)第5 s末,回路中的电流多大?
(3)第5 s末,作用在cd杆上的水平外力多大?
(1)
=0.4 V (2) 0.8 A. (3) 0.164 N.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824175417561321.png)
试题分析:(1)5 s内的位移:x=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824175417763338.png)
5 s内的平均速度
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824175418060270.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824175418263368.png)
(也可用
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824175418060270.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824175418809541.png)
故平均感应电动势
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824175417561321.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824175418060270.png)
(2)第5 s末:v=at=10 m/s
此时感应电动势:E=BLv
则回路电流为:I=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824175419869440.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824175420197535.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824175420493651.png)
(3)杆匀加速运动,则F-F安=ma
即F=BIL+ma=0.164 N.
点评:本题是电磁感应中的力学问题,综合了电磁感应、电路、力学等知识.考查分析和解决综合题的能力.
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目