题目

       — Morning, boys and girls! Please try your best in today’s exam! Good luck to all of you! — ________        A. Sorry, I won’t.            B. Thanks! C. Never mind。                    D. Congratulations! 答案：B 小灯泡L1和L2上都标有“3V”字样，其灯丝电阻分别为R1和R2，它们的电流随电压变化关系如图所示。有（ ）A．L1的额定功率为0.36W B．L2的阻值R2为0.72?C．若把小灯泡L1和L2并联在电源电压为2V的电路中工作，则小灯泡L2的实际功率是0.12W D．若把小灯泡L1和L2串联在电源电压为3V的电路中工作，则小灯泡L1的实际功率是0.16W