问题 实验题

在“描绘小灯泡的伏安特性曲线”的实验中,使用的小灯泡为“6 V 、3 W”,其他供选择的器材有:

电压表V1(量程6 V,内阻20 kΩ)

电流表A1(量程3 A,内阻0.2 Ω)

电流表A2(量程0.6 A,内阻1 Ω)

变阻器R1(0~1000 Ω,0.5 A)

变阻器R2(0~20 Ω,2A)

学生电源E(6 V~8 V)

开关S及导线若干

实验中要求在电压表0~6 V范围内读取并记录下12组左右不同的电压值U和对应的电流值I,以便作出伏安特性曲线,则在上述器材中,电流表应选_______,按正确方法连接电路电阻的测量值和真实值相比_______(填偏大、偏小、不变),变阻器应选_______。在下边方框中画出此实验的原理图。

答案

A2,偏小,R2

阅读理解

When I was a boy growing up in New Jersey in the 1960s, we had a milkman delivering milk to our doorstep. His name was Mr. Basille. He wore a white cap and drove a white truck. As a 5-year-old boy, I couldn’t take my eyes off the coin changer fixed to his belt. He noticed this one day during a delivery and gave me a quarter out of his coin changer.

Of course, he delivered more than milk. There was cheese, eggs and so on. If we needed to change our order, my mother would pen a note—“Please add a bottle of buttermilk next delivery”—and place it in the box along with the empty bottles. And then, the buttermilk would magically(魔术般)appear.

All of this was about more than convenience. There existed a close relationship between families and their milkmen. Mr. Basille even had a key to our house, for those times when it was so cold outside that we put the box indoors, so that the milk wouldn't freeze. And I remember Mr. Basille from time to time taking a break at our kitchen table, having a cup of tea and telling stories about his delivery.

There is sadly no home milk delivery today. Big companies allowed the production of cheaper milk thus making it difficult for milkmen to compete (竞争). Besides, milk is for sale everywhere, and it may just not have been practiced to have a delivery service.

Recently, an old milk box in the countryside I saw brought back my childhood memories. I took it home and planted it on the back porch (门廊). Every so often my son's friends will ask what it is. So I start telling stories of my boyhood, and of the milkman who brought us friendship along with his milk.

小题1:Mr. Basille gave the boy a quarter out of his coin changer     .

A.to show his magical power

B.to pay for the delivery

C.to satisfy his curiosity

D.to please his mother小题2:What can be inferred from the fact that the milkman had the key to the boy's house?

A.He wanted to have tea there.

B.He was a respectable person.

C.He was treated as a family member.

D.He was fully trusted by the family.小题3:Why does home milk delivery no longer exist?

A.Nobody wants to be a milkman now.

B.It has been driven out of the market.

C.Its service is getting poor.

D.It is forbidden by law.小题4:Why did the author bring back home an old milk box?

A.He missed the good old days.

B.He wanted to tell interesting stories.

C.He needed it for his milk bottles.

D.He planted flowers in it.

单项选择题