题目内容
如图甲所示,为一种调光台灯电路示意图,它通过双向可控硅电子器件(不分得电压)实现了无级调节亮度.给该台灯接220V的正弦交流电后加在灯管两端的电压如图乙所示,则此时交流电压表的示数为( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250023527669982.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250023527822412.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250023527823266.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250023527669982.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250023527822412.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250023527823266.jpg)
A.220 V | B.110 V | C.![]() | D.![]() |
B
试题分析:交变电流的有效值是根据电流的热效应来规定的.当如图乙所示的电压加在台灯上时,设电压的有效值为U,台灯电阻为R,在一个周期内放出的电热为Q,则有
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250023528441000.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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