题目内容
如右图所示,理想变压器输入端接在电动势为ε,内阻为r的交流电压上,输出端接负载R,如果要求负载R上消耗的电功率最大,则 ( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241301293711565.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241301293711565.jpg)
A.变压器原副线圈的匝数比为![]() |
B.变压器原副线圈的匝数比为![]() |
C.负载R上消耗的电功率最大值是![]() |
D.负载R上消耗的电功率最大值是![]() |
C
设原副线圈的匝数分别为n1,n2,电流分别为I1,I2,电压分别为U1,U2,则:
电阻R消耗的电功率为
,即![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130129871761.png)
可见当
时,P有最大值
此时
,则
又因:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130130229169.png)
代入上述所求I1,I2得:
,说明当
时,电阻R消耗功率最大。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130129808492.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130129839561.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130129871761.png)
可见当
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130129902475.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130129917668.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130129949626.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130129980667.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130130011657.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130130229169.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130130276465.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130130432553.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130130448533.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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