问题 问答题 简答题

试述太阳能电池的基本原理。

答案

参考答案:

太阳能电池工作原理的基础是半导体p-n结的光生伏打效应,就是当物体受到光照时,物体内的电荷分布状态发生变化而产生电动势和电流的效应。当太阳光或其他光照射半导体p-n结时,就会在p-n结的两边出现电压,叫做光生电压,使p-n结短路,就会产生电流。

阅读理解

阅读理解。

     A small man with a fat stomach got on the train at the last station before the frontier (边境). He

carried a paper bag. And four feet of ducks could be seen under the cover. The man found an empty

seat, put the bag in the middle of the floor, took out a newspaper and began to read. Then a policeman

came in. Of course he saw the bag with ducks' legs at once and said, "Whose is that bag?" Nobody

answered. The policeman repeated the question, and said, "I'll have to take it away from the owner.

Food mustn't be taken out of the country." "Well, then," said the small man with a fat stomach. "Hurry

up and take it. We want to go home." The policeman took the bag and went on to the next carriage.

      At the next station, when they were safely across the frontier, the small man got up, smiled at the

other passengers and said, "I hope they'll enjoy the ducks' feet. The rest in the bag was nothing but

rubbish." Then he opened his coat and pointed to another bag he was carrying under it. It was tied

tightly (紧紧地) over the stomach, which was not really fat. "The rest of the ducks is here," he said

with a smile on his face. With these words, he got off the train. But while he was happily walking to

the exit with the bag in his hands, a policeman came up to him, saying, "Hey, man! Foreign food

mustn't be brought in."

1. Where did the man put his paper bag after he got on the train?

A. In an empty seat.

B. Near his newspaper.

C. In the middle of the floor.

D. He gave it to the policeman.

2. The first policeman took the paper bag away because _____________.

A. he wanted to find the owner of the bag

B. he enjoyed the ducks feet in the bag

C. the bag was put in a wrong place in the carriage

D. food can't be taken abroad

3. How many ducks did the man take with him when he got on the train?

A. 1.

B. 2.

C. 3.

D. 4.

4. In the end the small man ____________.

A. failed to take his food home

B. crossed the frontier with two paper bags

C. took the ducks safely home

D. hid his ducks under his coat again

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