题目内容
如图所示,理想变压器输入端接在电动势随时间变化、内阻为r的交流电源上,输出端接理想电流表及阻值为R的负载,变压器原、副线圈匝数的比值为
。如果要求负载上消耗的电功率最大,则下列说法正确的是
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250048189978002.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004818951434.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250048189978002.jpg)
A.交流电源的效率为50% | B.电流表的读数为![]() |
C.负载上消耗的热功率为![]() | D.该交流电源电动势的瞬时值表达式为![]() |
AB
试题分析:将变压器、电阻R及电流表部分等效与电源的外电路R/,当电源的外电路电阻R/等于电源内阻r时,电源输出功率最大,负载R上得到的功率也最大,此时电源的内电压等于外电压,电源的效率
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004819075900.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004819091827.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250048191071614.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004819013736.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250048191381176.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250048191531126.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250048191691022.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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