题目内容
如图所示,在匀强磁场中有一个“π”形导线框可绕AB轴转动,已知匀强磁场的磁感应强度B=
T,线框的CD边长为20 cm,CE、DF长均为10 cm,转速为50 r/s.若从图示位置开始计时:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408242132335962724.png)
(1)写出线框中感应电动势的瞬时值表达式;
(2)在e-t坐标系中作出线框中感应电动势随时间变化关系的图像.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824213233097545.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408242132335962724.png)
(1)写出线框中感应电动势的瞬时值表达式;
(2)在e-t坐标系中作出线框中感应电动势随时间变化关系的图像.
(1)e=
cos 100πt V(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408242132352342074.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824213234439439.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408242132352342074.jpg)
试题分析:(1)线框转动,开始计时的位置为线圈平面与磁感线平行的位置,在t时刻线框转过的角度为ωt,此时刻e=Bl1l2ωcos ωt即e=BSωcos ωt,其中B=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824213233097545.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824213233097545.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824213234439439.png)
(2)线框中感应电动势随时间变化关系的图像如图所示.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408242132396653023.jpg)
点评:感应电动势的瞬时值表达式有三个要素:最大值,角速度和初相位,只有从中性面开始计时时,瞬时值表达式才为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824213240117640.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目