问题 实验题

某待测电阻的阻值大约为10Ω,为测量其阻值,实验室提供了下列可选用的器材

A.电流表A1(量程300mA,内阻约1Ω)

B.电流表A2(量程0.6A,内阻约3Ω)

C.电压表V1(量程3.0V,内阻约5kΩ)

D.电压表V2(量程15.0V,内阻约15kΩ)E.滑动变阻器R1(最大阻值为50Ω)

F.滑动变阻器R2(最大阻值为500Ω)

G.电源E(电动势4V,内阻可忽略)

H.电键、导线若干

①为了尽可能提高测量准确度,应选择的器材为(只需填写器材前面的字母即可)电流表         ;电压表        ;滑动变阻器         .

②在下列给出的方框中画出合理的实验电路图

答案

ACE

题目分析:电阻的大小容易受到温度的影响,所以电路中的电流一般要求不能过大,所以选择电流表A,当滑动变阻器电阻为零时,待测电阻两端的电压不过为3V,所以采用电压表C,滑动变阻器的选择原则是操作方便,所以一般选取和被测电阻相接近的,故选E,

点评:本题应明确实验的原则应以安全、准确为主,若量程过大将会导致测量结果不准确;故此题以电流表代替了电压表使用,读出电流值再通过计算得出电压值.

阅读理解

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In 1909 an English newspaper offered £ 1,000 to the first man to fly across the English Channel in an aeroplane. Today, modern jets cross it in minutes. But at that time it still seemed a good distance. The race to win the money soon became a race between two men. Both were very colourful.

One was Louis Bleriot. He owned a factory in France that made motor car lamps. He was already well known as a pilot because he had had accidents several times. Some people laughed at him. One man said, “He may not be the first to fly across the Channel but he will certainly be the first to die in an accident!” But Bleriot was really a good and brave pilot. He also had many good ideas about aeroplane design.

The other man was Hubert Latham. He was half French and half English. He took up flying when his doctors told him he had only a year to live. “Oh, well,” he said, “if I’ m going to die soon, I think I shall have a dangerous and interesting life now.” Latham was the first to try the flight  across the Channel. Ten kilometres from the French coast, his plane had some trouble. It fell down into the water and began to sink under the water. A boat reached Latham just in time. He was sitting calmly on the wing and was coolly lighting a cigarette. Bleriot took off six days later. He flew into some very bad weather and very low cloud. He somehow got to the English side and landed in a farmer’s field. When he did so, a customs (海关) officer rushed up to his plane. Planes have changed since then, but customs officers have not. “Have you anything to declare(报关)?” The officer demanded.

48. Bleriot was well known as a pilot because ____ .

A. he was unusually brave

B. he was quite rich

C. he had many good ideas about aeroplane design

D. he had had a few accidents

49. Why did Hubert Latham want to fly across the Channel?

A. He thought he could manage it easily.

B. He wanted to be the first one to cross the Channel.

C. He knew he only had a year to live.

D. He had always been interested in flying.

50. Which of the following is NOT true?

A. Latham became a pilot on the doctor’s advice.

B. He was told he could live another year.

C. His plane had some trouble.

D. He was saved by a boat when his plane was sinking.

单项选择题