题目内容
如图所示,A为电解槽,M为电动机,N为电炉子,恒定电压U=12 V,电解槽内阻rA=2 Ω,当S1闭合,S2、S3断开时,电流表A示数为6 A;当S2闭合,S1、S3断开时,A示数为5 A,且电动机输出功率为35 W;当S3闭合,S1、S2断开时,A示数为4 A.求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241527443243588.jpg)
(1)电炉子的电阻及发热功率各多大?
(2)电动机的内阻是多少?
(3)在电解槽工作时,电能转化为化学能的功率为多少?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241527443243588.jpg)
(1)电炉子的电阻及发热功率各多大?
(2)电动机的内阻是多少?
(3)在电解槽工作时,电能转化为化学能的功率为多少?
(1)2Ω 72W (2)1Ω (3)16W
试题分析:(1)电炉子为纯电阻元件,由欧姆定律
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152744371509.png)
得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152744512721.png)
其发热功率为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152744699999.png)
(2)电动机为非纯电阻元件,由能量守恒定律得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152744839944.png)
所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241527449801150.png)
(3)电解槽工作时,由能量守恒定律得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241527451041062.png)
点评:注意纯电阻电路与非纯电阻电路在的区别
![](http://thumb2018.1010pic.com/images/loading.gif)
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