题目

滑动变阻器最大阻值为当、均闭合且滑片滑到b端时，电流表、的示数分别为乙、丙所示；当、均断开且滑片P置于变阻器的中点时，电流表的示数为0.4A，求：(1)电源的电压；   (2)的电阻；(3)灯L的电阻；     (4)整个电路消耗的最小电功率； 答案：(1)(2)(3)(4)∵当电路中电阻最大时，消耗的电功率最小∴当、断开，滑片P滑到b端时电路中电阻最大，最大值为：最小功率值为：.   2.88Before you go to another country, it is a great help if you know the language and some of the customs of the country.When people meet each other for the first time in Britain, they say “Hello!” or “Nice to meet you!”, and shake hands. Usually they do not shake hands when they just meet or say goodbye. But they shake hands after they haven’t met for a long time or when they will be away from each other for a long time.Last year a group of German students went to England for a holiday. Their teacher told them that English people hardly shake hands. So when they met their English friends at the station, they kept their hands behind their backs. The English students had learned that the Germans shake hands as often as possible, so they put their hands in front and got ready to shake hands with them. It made both of them laugh.1.If you want to travel, it is _________ for you to know the language and some of the customs of the country you are going to visit.A. rude B. comfortable C. helpful D. difficult2.English people usually shake hands when they ______.A. meet every time B. meet for the first timeC. say goodbye to each other D. say hello to each other3.Usually English people don’t shake hands _____.A. when they will be away for a long time B. when they say “How do you do?”C. when they just meet or say goodbye D. after they haven’t met for a long time4.According to the passage, which of the following is TRUE?A. The Germans shake hands as often as possible.B. The English people like shaking hands very much.C. The Germans hardly shake hands.D. Neither the English people nor the Germans like shaking hands.5.This passage is about ______.A. shaking hands in Germany B. languagesC. customs D. German students in England