题目内容
电源的效率η定义为外电路电阻消耗的功率与电源的总功率之比.在测电源电动势和内电阻的实验中得到的实验图象如图所示,图中U为路端电压,I为干路电流,a、b为图象上的两点,相应状态下电源的效率分别为ηa、ηb.由图可知ηa、ηb的值分别为( )![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082414245999113376.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241425000381417.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082414245999113376.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241425000381417.png)
D
本题主要考查电源效率的理解与计算.在闭合电路中,电源的效率![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241425001005104.png)
也是外电压与电动势之比,也等于外电阻与总电阻之比.设图中每一小格数值为k,由图象知,电源的电动势为6kV,a和b对应的外电压分别是4kV和2kV,由此知D项正确.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241425001005104.png)
也是外电压与电动势之比,也等于外电阻与总电阻之比.设图中每一小格数值为k,由图象知,电源的电动势为6kV,a和b对应的外电压分别是4kV和2kV,由此知D项正确.
![](http://thumb2018.1010pic.com/images/loading.gif)
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