问题 选择题

如图所示的四个实验装置中,用来探究电磁感应现象的是(  )

A.

B.

C.

D.

答案

A、装置中,若开关闭合,金属棒左右切割磁感线运动,此时电路中就会产生电流,是电磁感应实验装置,故A符合题意;

B、装置将通电导线放在小磁针之上,是用来研究通电导体周围是否存在磁场的实验,即奥斯特的电流磁效应实验,故B不符合题意;

C、装置让通电导体放在磁场中,它会受到力的作用,这是用来研究磁场对电流的作用(或通电导体在磁场中受力)的实验,故C不符合题意;

D、装置让通电线圈放在磁场中,它会受到力的作用,这是用来研究磁场对电流的作用(或通电导体在磁场中受力)的实验,即电动机的原理实验,故D不符合题意.

故选A.

选择题

11.Every boy and every girl ___ a new book.

A. are given        B. is given        C. has given         D. have given

12.Each of us ___ a dictionary of this kind.  

We each ___ a dictionary of this kind.

A. has; have        B. have ; have       C. has; has         D. have ; has

13. “All ___ present and all ___ going on well,” our monitor said.

A. is; are           B. are ; are           C. are; is           D. is; is

14. The young ___ happy to give their seats to the old.    

A. is             B. are                C. has            D. have

15. Over sixty percent of the city ____ destroyed in the war. 

Thirty-five percent of the doctors ____ women.   

A. was; was         B. was; were         C. were; were       D. were; was

16.The shoes ___ mine.     This pair of shoes ___ my brother’s.

A. are; is             B. is; is            C. are; are             D. is; are

17.Large quantities of cotton ___ shipped all over the world already.

A large quantity of bamboo ___ used for pipes to carry water.

A. has been; are        B. has been; is      C. have been; is      D. have been; are

18.Setting fire to the public buildings ___ highly dangerous and forbidden by law.

A. are                B. is            C. has               D. were

19. The only means to achieve success ___ to appeal to arms.  

A. is             B. are              C. were                D. have

20. Whisky and soda ___ always his favourite drink.

A. are            B. is              C. be                  D. were

单项选择题