问题 问答题

某学习小组的同学拟探究小灯泡L的伏安特性曲线,可供选用的器材如下:

①小灯泡L,规格“4.5V.0.5A”;

②电流表A,量程0.6A,内阻r约为0.2Ω;

③电压表V,量程15V,内阻约为15kΩ;

④滑动变阻器R,阻值范围0~10Ω;

⑤学生电源E,电动势6V,内阻不计;⑥开关S及导线若干.

(1)甲同学设计了如图1所示的电路进行测量,请按照图1电路图把图2实物图中未完成的连线补充完整.

(2)乙同学经分析发现甲同学实验精度不高,又从实验室找来Ig=100μA,Rg=1000Ω的灵敏电流计和电阻箱(0-99999.9Ω),想把灵敏电流计改装成量程为5V的电压表,需要把电阻箱调成______Ω的阻值,并与灵敏电流计______(填“串”或“并”)联在电路中来替代实验中的电压表.

(3)乙同学用改装的电压表实验得到数据,现要以纵坐标表示通过电流表A的电流I,横坐标表示通过灵敏电流计的电流IG,画出I-IG图线,他已经把数据画在坐标纸上,请帮他把图线画出来.

(4)乙同学通过查找资料发现同等型号的小灯泡的灯丝在27℃时电阻是2.1Ω,并且小灯泡灯丝电阻值与灯丝温度的关系为R=k(273+t),k为比例常数.请估算灵敏电流表的电流IG=60μA时该灯泡灯丝的温度约为______℃.

答案

(1)连接如图:

(2)设改装后的电压表为R,则R=

U
Ig
=50000Ω,故R=R-Rg=49000Ω.

(3)连成光滑曲线如图:

(4)840~870均可 

故答案为:(1)如图;(2)49000,串联;(3)如图,连成折线的不给分,连成光滑曲线即可给分(4)840~870均可

阅读理解

It seems school children all over the world are not satisfied with their school food. Cherie Blair, the wife of Prime Minister Tony Blair, said that she would prepare a packed lunch for her son if school dinners do not improve. So what do students of your age eat for lunch at school?

Japan

High schools have dining halls, which serve everything from noodles to rice, but not hamburgers and chips. Other children bring food from home such as cold rice balls, meat or fish, and vegetables.

The United States

A common menu from a US school is made up of a hamburger with fried(油炸的)potatoes or roast chicken, fruit and cookies. School lunches must also provide food with protein(蛋白质),vitamin A, vitamin C, ironand calories.

Australia

Meat piesand hotdogs are all traditional dishes in Australian school shops. But as the nation pays more attention to children’s health, healthier foods have started to find their way onto school menus.

Many schools have used a traffic light system. The sale of red-labeled (标签) foods includingchocolate and soft drinks, is served only twice a week. Healthier green-labeled foods such as sandwiches, corn and watermelon, however are served every day.

In some schools, students have a choice of up to 89 foods to choose from, including popcorn and rice.

South Africa

Most of South Africa’s schools do not serve meals at all. Classes end at 1:30 pm and students get their own lunches. Many students bring food from home, usually sandwiches.

Fast food and fried food sell the best among students, which has led to a rise in obesity among children. But as more people began to realize the fact that being too fat may cause different illnesses, some schools in towns have led the way towards better nutrition(营养). Now students at these schools are provided with lunches of porridge(粥) with vegetables, such as cabbages, carrots and tomatoes.

小题1:Which belongs to red-labeled food in Australia?

A.sandwiches

B.apple juice

C.tomatoes

D.corn小题2:What does the underlined word ‘obesity’ in the last paragraph probably mean?

A.allowances(补贴)

B.sadness

C.nutrition

D.overweight小题3:What is the main idea of the passage?

A.Food served in the US is the best of all.

B.Schools should try to satisfy the needs of studemts.

C.Schools serve different foods from country to country.

D.School children all over the world dislike their school food.

单项选择题