题目内容
(改编)一正弦交变电压的电压u随时间t变化的规律如图所示。下列说法正确的是 ( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241322412571231.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241322412571231.png)
A.该交变电压的瞬时值表达式为u=10sin(50![]() |
B.该交变电压有效值约为7.1V |
C.将该交变电压接在匝数比为1∶2的理想变压器原线圈上,副线圈输出频率为50 Hz |
D.将该交变电压加在阻值R=20 Ω的白炽灯两端,电灯消耗的功率是5W |
AB
由图象知该交变电压的最大值为10V,周期为4×10-2s,其角频率
rad/s,其瞬时值表达式为u=10sin(50
t)V,A项正确;其有效值为5
V=7.1V,B项正确;该交变电压的频率
25 Hz,变压器不改变交流电的频率,C项错;计算白炽灯的功率要用有效值,
2.5W,D项错误。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824132241320778.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824132241288282.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824132241398336.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824132241429479.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824132241491628.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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