问题 问答题

有一个标有“12V、24W”的灯泡,为了测定它在不同电压下的实际功率和额定电压下的功率,需测定灯泡两端的电压和通过灯泡的电流,现有如下器材:

A.直流电源15V(内阻可不计)

B.直流电流表0~0.6A~3A(内阻0.5Ω、0.1Ω)

C.直流电流表0~300mA(内阻约5Ω)

D.直流电压表0~3V~15(内阻约3kΩ、15kΩ)

E.直流电压表0~25V(内阻约200kΩ)

F.滑动变阻器10Ω、5A

G.滑动变阻器1kΩ、3A

(1)实验台上已放置开关、导线若干及灯泡,为了完成实验需要从上述器材中再选用______(用序号字母表示).

(2)在答案卷上相应方框内画出最合理的实验电路图,并按设计的电路及合理的量程用黑色水笔替代导线将实物连好.

答案

(1)灯泡的规格为“12V、24W”,由此可知其额定电流为:I=

P
U
=
24W
12V
=2A,额定电压为:12V,因此电源选择A,电流表选择B,电压表选择D,该实验测定灯泡在不同电压下的实际功率和额定电压下的功率,需要多测量数据,因此滑动变阻器采用分压接法,故滑动变阻器选择F.

故答案为:ABDF.

(2)灯泡电阻较小,因此采用安培表外接法,同时滑动变阻器采用分压接法,由此可画出实验原理图如下所示:

根据原理图得出实物图如下所示:

单项选择题 A1/A2型题
阅读理解

We all love our children and we all know how competitive the world is these days. What’s it going to be like when our children leave school? Will they have the skills they need to stay ahead of the competition?

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You and your children can spend time together in a worthwhile pursuit (事业)—learning how to write. Forget the theme parks, the computer games, the expensive movies and interesting sports. If you want your children to have treasured memories of time spent with you, learn together.

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Don’t stand by while your child is left further and further behind.   

小题1:From the last two paragraphs, we can know the main purpose of the passage is_______

A.To encourage students to be better prepared for the future.

B.To list the qualities children must have for their future success.

C.To persuade parents to choose a writing course for their kids.

D.To explain the difficult situation children have to face at present.小题2:In the author’s opinion, ______.

A.speed-reading is the first step in a child’s formal education

B.children today waste too much time on games, movies and sports

C.children’s success depends much on good skills in reading and writing

D.writing helps people communicate more effectively in modern society小题3:What does the author think of writing as a form of communication now?

A.Important.

B.Funny.

C.Informal.

D.Old-fashioned.小题4:What’s the advantage of children’s learning together with their parents?

A.They will learn more quickly and accurately.

B.They will not be affected by games and sports.

C.It will encourage them to work for a higher pursuit.

D.They will have good memories of time spent with parents.