题目

如图所示，电源电压保持不变，闭合开关，将滑动变阻器的滑片P移到某位置时，电压表示数为，电流表示数为；再次移动滑动变阻器的滑片到另一位置时，电压表示数为，电流表示数变化了，下列结果正确的是（ ）A.的电阻为B.电源电压为C.的功率变化了D.的功率变化了 答案：【答案】AD【解析】由电路图可知，定值电阻R0与滑动变阻器R串联，电压表V测滑动变阻器R2两端的电压，电流表测电路中的电流；由欧姆定律的变式和串联电路电压规律可表示出滑片在不同位置时滑动变阻器两端的电压，定值电阻两端电压与电源电压间的关系，联立可计算得出与定值电阻R0的阻值及电源   A good book can teach you things I Rea^ Book beyond your class. It can open your eyes and clear your minds. If you want to get into a good reading habit,there are a number of ways to develop it.   Plan your time   You should give yourself at least thirty minutes in all for reading every day. When time is set,nothing can change it. For example,make it a habit to read during breakfast or lunch time.  Always carry a book   Wherever you go,take a book with you. When you leave the house,make sure that you always carry a good book as well as your school things. Remember that a book always stays with you.  Find a quiet place   Find a place in your home where you can sit in a comfortable chair. When you read a book,no one will trouble you. There should be no televisions,computers,music or e-ven noisy family members around you.   Have a library day   Have a library card,and you can read as many good books as possible in the library. Make it a weekly trip to the library.You can save a lot of money.    Blog it   One of the best ways to develop a good reading habit is to pul it on your blog (博客) .If you don't have one,create one. It's free .Ask your friends and family to go there to share your ideas and offer you suggestions.TitleSome ways to have a good reading 36 Plan your timeYou should read at least half a(n) 37  every clay. Make it a habit to 38  during breakfast or lunch time.Always 39  a bookMake sure a book always with you wherever you go.Find a quiet   placeFind a place at home with a 40  chair and without televisions, 41  ， music or noisy people around   you.Have a 42  dayIt is a very cheap way to read good books in the library. Go on a trip  to the library every 43  .Blog itIt 44  no money to create a blog. Your friends and family can share   your ideas and 45  you some suggestions online.36.   37.   38.   39.   40.  41.   42.   43.   44.   45.