问题 问答题

用湿抹布清洁电线、灯座,这样做是不允许的,为什么?

答案

答:潮湿的物体比干燥的物体电阻要小得多,由欧姆定律I=

U
R
知道,在电压一定的条件下,电阻越小,产生的电流越大,它一旦与电源、人体构成通路就会造成人体触电事故.所以这样做是不允许的.

判断题
阅读理解

Many people have to work on the weekend. Some people do not mind. Others think it is terrible.

  One man thinks that working on the weekend can be dangerous. He is Graham Coates. Mr Coates works in an office in Brighton, England.

  On Saturday, May 24, 1986, he went to the office to do some work. When he got on the lift(电梯), it stopped between floors. Mr Coates could not get out of the lift. He started to shout, but no one heard him. Then Mr. Coats remembered that it was a holiday in England. No one was going to come to work until Tuesday.

  There was nothing for him to do. He had to wait until one of his workmates came to work and found him. With nothing to eat or drink, Mr Coats ended up sleeping for most of the day.

  Now Mr. Coates says, "I only use lifts if they have telephones in them."

小题1:Mr. Coates thinks working on the weekend is_____.

A.interesting

B.terrible

C.happy

D.unhappy小题2:Mr. Coates stayed in the lift for_____.

A.about twenty hours

B.nearly two days

C.one week

D.more than sixty hours小题3:When Mr. Coates got out of the lift he_____.

A.was cold, weak, hungry and tired

B.wouldn't work there any more

C.said "I only use lifts if they have telephones in them."

D.went home at once小题4:Why could Mr. Coates not get out of the lift? Because _____.

A.it was broken

B.it was the weekend

C.it was in an office

D.it was a holiday小题5:In the lift, there was_________.

A.water

B.beer

C.telephone

D.nothing