问题 选择题

如图所示的实验中,其中能说明电动机工作原理的是(  )

答案

答案:D

题目分析:A、此实验探究的是电磁感应现象,它是发电机的原理,不符合题意;

B、此实验是奥斯特实验,说明电流周围存在磁场,不符合题意;

C、此实验探究的是电磁铁的磁性强弱与电流大小的关系,不符合题意;

D、此实验探究的是通电导体在磁场中受力运动的现象,符合题意.

故选D.

点评:电动机是将电能转化为机械能的机械,它在工作时要消耗电能,因此解题时观察图形中有无电源是此题的解题关键.

阅读理解

Before you hit ‘Enter’ on MSN, read this

It is often said that the language we use online is less formal than that we use in a letter, or in direct speech sometimes. This is true, but it can also make us in trouble sometimes.

The thing about online communication is that you have no idea what the person who is reading your messages is feeling. For this reason, it is always a good idea to be polite and cautious when writing e-mails or messages to your friends.

Chinese can be a direct language, but in English, people often talk about a subject in another way. So instead of saying “Please meet me here” or “Do this for me now”, English speakers usually go for indirect phrases like “Would it be possible”, “if you have time” or “It would mean a lot to me if…”

If you have a close friend, you may still run into trouble because of your jokes. If you have asked someone to do something and they need a bit more time, you might joke with him: “What? You still haven’t done it yet? What’s wrong with you?” While this seems funny to you, your friend may feel unhappy.

If you have foreign friends in different countries, the time difference can also be a factor. While you are waking up for class on Friday morning, they may be having a party on Friday night. You will be serious and they will, probably, be excited. So don’t be angry if they seem not to care about you. Just try to message them at the proper time.

小题1: According to the passage, we learn that our letters are more ______ than the e-mails.

A.formal

B.direct

C.different

D.funny小题2: As a language, Chinese is ______, but English is not.

A.polite

B.rude

C.direct

D.formal小题3: Why should we be polite and cautious while chatting online?

A.Because we mustn’t play jokes online.

B.Because our friends are easy to be angry.

C.Because it can help us avoid lots of troubles.

D.Because we can’t see our friends online.小题4: According to the passage, which of the following is right?

A.It is OK to connect your friend by MSN anytime.

B.Using the proper way to chat online is necessary.

C.Don’t ask your friend to do something for you by MSN.

D.Never play jokes with your friends.

单项选择题