问题 问答题 简答题

串联谐振与并联谐振在谐振时各有什么特性?

答案

参考答案:

串联谐振电路是纯电阻性,而且总阻抗最小,并等于R,电路中电流最大,电感上的电压等于电容上的电压,而且会使电压增大,即产生过电压。并联谐振时电路呈电阻性,电路中总电流最小,即为电流谐振。

单项选择题
完形填空

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第二节: 完形填空(共20小题, 满分20分)

Once upon a time, there was a boy who would go into the forest and gather food and herbal medicines(草药) with some of his fellows every spring. However, one year, a tiger  36  in the forest and no one dared go into the forest again. One day, the boy’s father became  37 , and the family couldn’t afford the  38  that the father needed. The boy decided to try and find some herbal medicines as well as some food in the forest.

It was a perfect sunny day. At first, it was quiet and  39  happened. But later, when the boy bent down to reach one more mushroom, he was suddenly pushed to the ground. A large shadow 40   him. He rolled over and looked  41  in shock as the tiger said in a deep voice. “You are my  42  . Say good-bye to this world.”  43  his sick father, the boy knew he couldn’t die. He quickly calmed down and put a(n)  44  into his mouth, and chewed and swallowed.Then he said, “45  you can kill and eat me, but I  46  you to know that these mushrooms are  47  poisonous(有毒的). You can eat me,  48  you will die too. My family will  49 me and find you. They will  50 your stomach and eat your meat. Your fine  51 will carpet the floor of a rich man’s house and your tiger bones will get a good  52  in the medicine shops. My family will have enough for a year or more and I will be given a good funeral(葬礼) and long53  .

The tiger hesistated. He saw the frightful mushrooms in the basket and  54  his appetite(胃口). He slowly walked away. The boy saved his own life with his quick  55 .

36.   A.broke out       B. woke up       C. showed up        D. set out

37.A.hungry          B. ill            C. angry        D.mad

38.A.love               B. medicine       C.care          D.doctors

39.A.anything          B. everything      C. nothing      D.something

40.A.covered           B.followed           C. caught    D. pushed

41.A.down           B. out              C. around       D. up

42.A.energy          B. power           C. enemy    D. supper

43.A.Looking after   B. Thinking of     C.Bringing back     D. Believing in

44.A.stone         B.leaf              C. mushroom        D. apple

45.A.Of course       B.No way           C. In the beginning         D. In any case

46.A.choose             B. wish            C. persuade    D. order

47.A.expensive          B. delicious        C. deadly       D. magic

48.A.as             B. so             C. but          D. because

49.A.look for            B. call for         C. take care of   D. get rid of

50.A.feed              B. open            C. sell            D. kick

51.A.head            B.tail              C. paws          D.skin

52.A.price              B. seller            C. reward        D. doctor

53.A.understood       B.encouraged       C.needed        D.remembered

54.A.lost            B. increased          C. regained     D. forgot

55.A.skill           B. warning         C. thinking      D.word