题目

如图甲是测定小灯泡电阻实验的实物图。 （1） 连接好电路，闭合开关前滑动变阻器滑片应该移到（填左或右）端。 （2） 闭合开关，移动滑动变阻器滑片，当电压表示数为2.80伏时, 电流表示数如图乙，此时小灯泡的电阻为欧。 （3） 在实验过程中，发现在开关闭合的情况下，小灯泡突然不亮，电压表和电流表均无示数。可能是电路某处开路，于是用一根导线检测，实验步骤和现象如下表。实验步骤导线两端接触位置电灯电流表电压 My secret of staying young is quite simple：devote your attention to the part of you that’s young and growing—your brain. Keep your mind awake and you will stay young all over. These are exciting times. Take an interest in the world around you，and make a point of learning one new thing every day. No matter how old you are ，it’s not too late to make your life more interesting. I know a housewife without knowledge in the past who made herself into an excellent industrial designer. I know an old electrical engineer who has become a highly paid artist. Get over the idea the you are too old to go back to school. I know a man who entered a medical college at 70. He got his degree with honors and became a famous doctor. Another man went to a law school at 71 and now is an active lawyer. No matter how old people are，staying young is easy for those who live in the future. You can do it if you are active enough to try. Keep your mind active and awake：that’s the only youth elixir.54. Which of the following best express the main idea of this passage？Staying young is the only youth elixir.Learning at least one new thing every day.Never too late to go back to school.The secret of staying young.55.  If you wish to stay young，above all ，you should        .A. keep your mind awake and active      B. make your life more interesting C. keep your mind from being harmed     D. keep in tough with other people56. The implied meaning of the passage is that        .A. anyone can learn to do something no matter how old they may be.B. the electrical engineer learned to be an artist to become famous.C. the man who entered the medical collage at 70 came out at the top of the list.D. every one can be successful if you try to learn no matter how old he may be57. The word “elixir”in the last sentence probably means something that can keep people        . A. healthy             B. wealthy            C. young               D. happy