问题 实验题

有一根长陶瓷管,其表面均匀地镀有一层很薄的电阻膜,管的两端有导电箍M和N,如图所示。用多用表电阻档测得MN间的电阻膜的电阻约为100,陶瓷管的直径远大于电阻膜的厚度。某同学利用下列器材设计了一个测量该电阻膜厚度d的实验。

A.刻度尺(最小分度为mm)

B.游标卡尺

C.电流表A1(量程0~300mA,内阻约0.2)

D.电流表A2 (量程0~100mA,内阻约0.6)

E.电压表V1 (量程10V,内阻约5k)

F.电压表V2 (量程5V,内阻约3k)

G.滑动变阻器R1 (阻值范围0~50,额定电流1.5A)

H.滑动变阻器R2 (阻值范围0~1.5K,额定电流1A)

I.电源E (电动势9V,内阻可不计)

J.开关一个,导线若干

(1)他用毫米刻度尺测出电阻膜的长度为l,用游标卡尺测量该陶瓷管的外径D。为了比较准确地测量电阻膜的电阻,且调节方便,实验中应选用电流表______________,电压表______________,滑动变阻器______________。(填写器材前面的字母代号)

(2)画出测量电阻膜的电阻R的实验电路图。

(3)若电压表的读数为U,电流表的读数为I,镀膜材料的电阻率为,计算电阻膜厚度d的数学表达式为:d=______________(用所测得的量和已知量的符号表示)。

答案

(1)D,E,G

(2)

(3)

阅读理解

The question of what children learn, and how they should learn, is continually being debated and redebated. Nobody dares any longer to defend the old system, the learning of lessons parrot-fashion, the grammar-with-a-whip system, which was good enough for our grandparents. The theories of modem psychology have stepped in to argue that we must understand the need of children. Children are not just small adults; they are children who must be respected as much.

Well, you may say, this is as it should be, a good idea. But think further. What happens? "Education" becomes the responsibility not of teachers, but of psychologists (心里学家). What happens then? Teachers worry too much about the psychological implications (暗示) of their lessons, and forget about the subjects themselves. If a child dislikes a lesson, the teacher feels that it is his fault, not the child’s. So teachers worry whether history is "relevant" to modern young children. And do they dare to recount stories about violence? Or will this make the children themselves violent? Can they tell their classes about children of different races, or will this encourage racial hatred? Why teach children to write grammatical sentences? Verbal expression is better. Sums? Arithmetic? No: Real-life mathematical situations are more understandable.

You see, you can go too far. Influenced by educational theorists, who have nothing better to do than to write books about their ideas, teachers leave their teacher-training colleges filled with grand, psychological ideas about children and their needs. They make elaborate, sophisticated (精致的,复杂的) preparations and try out their "modem methods" on the long-suffering children. Since one "modem method" rapidly replaces another the poor kids will have had a good bellyful by the time they leave school. Frequently the modem methods are so sophisticated that they fail to be understood by the teachers, let alone the children; even more often, the relaxed discipline so essential for the " informal" feelings the class must have, prevents all but a handful of children from learning anything.

8. People do not dare defend the old system mainly because under the old system________.

A. too much grammar was taught to children     B. children were spoiled (宠坏)

C. children were treated as grown-ups          D. children were made to learn passively(被动的)

9. What view do the modem psychologists hold?

A. Children must be understood and respected.

B. Children are small adults and know what they need.

C. Children are better off without learning lessons.

D. Education of children is the responsibility of psychologists.

10. What happens when teachers pay too much attention to the psychology of their lessons?

A. They find that the children dislike the lessons.

B. They tend to blame students for their failure.

C. They do not pay enough attention to the actual lessons.

D. They no longer want to teach children history.

11. Grammatical sentences are regarded as unimportant because ________.

A. it is better to use verbs only

B. words are said out of natural feelings only

C. talking freely and naturally without sentences is a better form of expression

D. it is felt that formal grammar rules might cause unnatural expressions

12. According to the passage, the modern methods are understood by ________.

A. neither teachers nor pupils      B. only a handful of teachers and pupils

C. the more sophisticated teachers  D. everyone who enjoys the relaxed discipline of the informal classes

单项选择题