题目

测定小灯泡的额定功率，电路如图所示（图中未标出电流表、电压表的符号），已知灯泡的额定电压为2.5伏特．（1）在下面右图的两圆圈中填上所用电流表和电压表的符号．（2）闭合开关之前，变阻器的滑动片P应置于________端（填a或b），实验过程中，变阻器的作用是_______________．（3）当灯泡正常发光时，灯泡两端的电压应为_________伏特，若电流表的示数如图所示，则通过灯泡的电流强度为_______安培，灯泡的额定功率为_______瓦特请听下面一段材料，回答第1-3题。 1. What does the woman want to know?A. The best way to go to New York.B. The quickest way to go to New York.C. The cheapest way to go to New York.2. How much does it cost the woman to go to New York by bus?A. $5.       B. $15.        C. $50. 3. What do we know from the conversation?A. The woman will go to New York by bus.B. It will take the woman five hours to go to New York by bus.C. The woman won’t go to New York by bus.