问题 选择题

如图所示的电路中,电源电压不变,只闭合开关S1时,电压表V1与V2的示数之比为3∶2;只闭合开关S2时,电压表V1与 V2的示数之比为5∶3,则R1与R2的电阻之比为

A.3∶5

B.2∶3

C.4∶3

D.5∶3

答案

答案:C

题目分析:只闭合开关S1时,等效电路如图a所示;只闭合开关S2时,等效电路如图b所示.

        

观察图a可知R1与R0串联,V1测串联电路总电压(即电源电压),V2测R1两端电压,串联电路中电压与电阻成正比,所以结合题意得1,观察图b同理可得2

解12两式得R1∶R2=4∶3,对照各选项,C正确,选填C。

阅读理解

Mike was ten years old and he went to the Ashland School. He was very good at football, so he was chosen(被选中) by the school team. He always played very well in the matches, and he scored a lot of goals (得分很多). One day Mike said to his parents, “we will play football with the Gum Tree School .Will you come and cheer us on?” And they agreed to come.

The match was in the park. The Gum Tree School team wore green shirts and blue shorts (短裤), and Mike’s team wore white shirts and red shorts. In the first two minutes of the match, Mike ran with the ball and kicked it into the goal. All the Ashland School boys and their families were very excited about it.

After that, Mike scored two goals before half time. Then in the second half of the match he almost scored another goal, but he kicked the ball with his foot lightly , and the goalkeeper caught it easily and threw it out.

After the match, Mike’s father said to him, “You missed a good chance (机会) to score another goal, Mike. Why did you kick it lightly?”

“Because there were tears (眼泪) in the goalkeeper’s eyes,” Mike answered.

小题1:Mike was chosen in the school team because he_____________ .

A.studied well

B.ran fast

C.like basketball

D.played football well小题2:What color shirts did Mike’s team wear?

A.Blue

B.Green

C.Red

D.White小题3:How many goals did Mike score in the match? .

A.Two

B.Four

C.Three

D.Five小题4:What does the word” goalkeeper” mean in the third paragraph? .

A.教练

B.守门员

C.裁判

D.观众小题5:From the passage we know ______________

A.Mike’s farther didn’t like playing football

B.the Gum Tree School Team lost the match because of the goalkeeper

C.the goalkeeper was happy when they won the match

D.Mike was a good player and was kind to others

单项选择题