题目内容
如图5所示,一个匝数为10的矩形线圈在匀强磁场中绕垂直于磁场的轴匀速转动,周期为T.若把万用电表的选择开关拨到交流电压挡,测得a、b两点间的电压为20 V,则可知:从中性面开始计时,当t=T/8时,穿过线圈的磁通量的变化率约为 ( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241416281383578.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241416281383578.jpg)
A.1.41 Wb/s | B.2.0 Wb/s |
C.14.1 Wb/s | D.20.0 Wb/s |
B
由于电压表测量的是交变电流的有效值,由此可以计算出交变电压的最大值为Em=
E=20
V.
交变电压的瞬时值表达式为:e=20
sin
t
当t=T/8时的瞬时值为:e=20 V
由法拉第电磁感应定律知,对应该时刻磁通量的变化率为
=2.0 Wb/s,故选项B是
正确的.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141628170344.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141628170344.png)
交变电压的瞬时值表达式为:e=20
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141628170344.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141628404504.png)
当t=T/8时的瞬时值为:e=20 V
由法拉第电磁感应定律知,对应该时刻磁通量的变化率为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141628482508.png)
正确的.
![](http://thumb2018.1010pic.com/images/loading.gif)
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