题目内容
(11分)如图所示的电路中,R1=1Ω,R2=6Ω,电源内阻r=1Ω,若开关闭合后通过电源的电流为3A,铭牌上标有“6V 12W”的电动机刚好正常工作,求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250030572282739.jpg)
(1)流过R2上的电流为多少?
(2)电源电动势为多少?
(3)若电动机线圈电阻为,电动机输出功率为多少?
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250030572282739.jpg)
(1)流过R2上的电流为多少?
(2)电源电动势为多少?
(3)若电动机线圈电阻为,电动机输出功率为多少?
(1) 1A (2)12V (3)10W
试题分析:(1)由题意可知根据部分电路欧姆定律得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003057243844.png)
(2)通过电动机的电流为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003057259941.png)
流过电源的电流
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003057274717.png)
由闭合电路欧姆定律可得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250030572901166.png)
(3)电动机的输入功率
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003057306954.png)
电动机内阻消耗的功率
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250030573211050.png)
电动机的输出功率
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003057337982.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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