Question

如圖所示是家用電飯煲的電路圖．將電飯煲接到穩(wěn)壓電源上，當(dāng)開關(guān)接通“加熱”檔時，電熱絲以額定功率給食物加熱，當(dāng)食物蒸熟后，開關(guān)接通“保溫”檔，給食物保溫，這時電熱絲的功率為其額定功率的，電流為1.40A，已知分壓電阻的       阻值R=100Ω．求：                                                                                          

（1）保溫時，電阻R兩端的電壓．                                                                                

（2）穩(wěn)壓電源輸出的電壓．                                                                                           

（3）電熱絲的額定功率．                                                                                              

                                                                                                       

                                                                                                                                       

Answer 1

（1）電阻R兩端的電壓為

U_R=IR=1.40×100=140（V）                             

（2）設(shè)電熱絲的電阻為r，電源輸出電壓為U，則

（ ）²r=

解得：r=50Ω                                         

所以電源電壓為U=I（R+r）=1.40×（100+50）=210（V）  

（3）電熱絲的額定功率為

P===882（W）         

答：（1）保溫時，電阻R兩端的電壓為140V；

（2）穩(wěn)壓電源輸出的電壓為210V；

（3）電熱絲的額定功率為882W．