问题 选择题

在实验室,某同学发现一个电流表有两个量程,大量程是0~9A,小量程模糊不清.为了测量小量程是多少,她先用大量程接入电路,指针位置如图(a)所示,然后再改用小量程接入同一电路,指针指示如图(b)所示,则电流表的小量程为(  )

A.0~0.6A

B.0~1A

C.0~2A

D.0~3A

答案

大量程的每一个大格是3A,每一个小格是0.3A,示数是1.5A,

大小量程的电流表接入的是同一电路,示数应该是相同的,

b图中指针的位置是1.5A,

所以,小量程为0~3A.

故选D.

选择题
单项选择题

Time spent in a bookshop can be most enjoyable, whether you are a book-lover or merely there to buy a book as a present. You may even have entered the shop just to find shelter from a sudden shower. But the desire to pick up a book with an attractive dust-jacket is irresistible. You soon become absorbed in some book or other, and usually it is only much later that you realize that you have spent far too much time there.

This opportunity to escape the realities of everyday life is, I think, the main attraction of a bookshop. There are not many places where it is possible to do this. A music shop is very much like a bookshop. You can wander round such places to your heart’s content. If it is a good shop, no assistant will approach you with the inevitable greeting: "Can I help you, sir" You needn’t buy anything you don’t want. In a bookshop an assistant should remain in the background until you have finished browsing. Then, and only then, are his services necessary.

You have to be careful not to be attracted by the variety of books in a bookshop. It is very easy to enter the shop looking for a book on, say, ancient coins and to come out carrying a copy of the latest best-selling novel and perhaps a book about brass-rubbing -- something which had only vaguely interested you up till then. This volume on the subject, however, happened to be so well illustrated and the part of the text you read proved so interesting that you just had to buy it. This sort of thing can be very dangerous. Booksellers must be both long suffering and indulgent.

There is a story which wei1 illustrates this. A medical student had to read a textbook which was far too expensive for him to buy. He couldn’t obtain it from the library and the only copy he could find was in his bookshop. Every afternoon, therefore, he would go along to the shop and read a little of the book at a time. One day, however, he was dismayed to find the book missing from its usual place and about to leave when he noticed the owner of the shop beckoning to him. Expecting to be reproached, he went toward him. To his surprise, the owner pointed to the book, which was tucked away in a corner. "I put it there in case anyone was tempted to buy it," he said, and left the delighted student to continue his reading.

It can be learned from the text that an assistant should offer you help()

A. as soon as you have entered the shop

B. just before you finish browsing

C. only when you have finished reading

D. when he leads you to a particular section