题目内容
(1998年上海)如图17-4-13所示,理想变压器原副线圈匝数之比为n1∶n2=2∶1,原线圈接200 V交流电源,副线圈接额定功率为20 W的灯泡L,灯泡正常发光.当电源电压降为180 V时,灯泡实际消耗功率与其额定功率之比为________,此时灯泡中的电流为________A.(设灯泡电阻恒定)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241216412991818.gif)
图17-4-13
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241216412991818.gif)
图17-4-13
0.81,0.18
接200 V时,
,U2=
×200 V=100 V,P额=
;接180 V时,U2′=
U1′=
×180 V=90 V,P′=
;
=0.81
P′=0.81×P额=0.81×20 W=16.2 W.P′=IU2′,I=
A=0.18 A.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121641299503.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121641315504.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121641331427.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121641346371.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121641362225.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121641596430.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121641689839.gif)
P′=0.81×P额=0.81×20 W=16.2 W.P′=IU2′,I=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121641705595.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目