题目

Yangjiang，a famous female writer，_____________for abut a month so far． A．died    B．has been dead    C．has been died 答案：B5．如图所示，电源电压保持不变，电阻R1=16Ω，R2=4Ω．当S1、S2都关闭时，电流表示数为2.5A；当开关S1、S2都断开时，小灯泡L消耗的电功率为1.0W．求：（1）电源两端电压U；（2）小灯泡L的电阻．