问题 选择题

下列说法错误的是(  )

A.电灯的开关,应接在火线和电灯之间

B.更换灯泡时,先断开开关

C.使用大功率的用电器时,应将用电器的金属外壳接地

D.选用电阻小、熔点低的合金丝作保险丝

答案

A、开关要控制灯泡时,开关和灯泡必须串联,开关接在火线上,开关断开时,灯泡停止工作,同时灯泡周围的导体都与火线断开,在更换灯泡时更安全.故该项说法正确,不符合题意.

B、更换灯泡时,为灯泡周围的导体都与火线断开,防止发生触电,应先断开开关;故该项说法正确,不符合题意.

C、使用大功率的用电器时,用电器外壳一般是金属,为防止“漏电”而发生触电事故,应将用电器的金属外壳接地;故该项说法正确,不符合题意.

D、电路中电流过大时,保险丝需产生较多的电热,应选用电阻大,熔丝的温度应短时间内达到的熔点而熔化,合金丝的熔点应低,所以该选项中说法错误,符合题意.

故选D.

写作题
阅读理解

We each have a memory(记忆力). That’s why we can still remember things after a long time. Some people have very good memories and they can easily learn many things by heart, but some people can only remember things when they say or do them again and again. Many of the great men of the world have got surprising memories.

A good memory is a great help in learning a language. Everybody learns his mother language when he is a small child. He hears the sounds, remembers them and then he learns to speak. Some children are living with their parents in foreign countries. They can learn two languages as easily as one because they hear, remember and speak two languages every day. In school it is not so easy to learn a foreign language because the pupils have so little time for it, and they are busy with other subjects, too.

But your memory will become better and better when you do more and more exercises.

小题1:、Some people can easily learn many things by heart because                .

A.they always sleep very well

B.they often eat good food

C.they read a lot of books

D.they have very good memories小题2:.、Everybody learns his mother language         .

A.at the age of six

B.when he is a small child

C.after he goes to school

D.when he can read and write小题3:.、Before a child can speak, he must              .

A.read and write

B.make sentences

C.hear and remember the sounds

D.think hard小题4:.、In school the pupils can’t learn a foreign language well because          .

A.they have no good memories

B.they have no recorders

C.they have too much time for it

D.they are busy with other subjects小题5:.、Your memory will become better and better          .

A.if you have plenty of good food

B.if you do more and more exercises

C.if you do morning exercises every day

D.if you get up early