问题 选择题

关于电源电动势,下面说法不正确的是(  )

A.并联在电源两极的电压表的示数一定等于电源电动势

B.电动势越大的电源,将其它能转化为电能的本领一定越大

C.电路接通后,电源两端的电压小于它的电动势

D.电动势只由电源本身的性质决定与外电路是否是纯电阻电路无关

答案

答案:A

题目分析:如果外电路中,只有电压表,电压表测量的是电源电动势大小,如果外电路中还有其它用电器,则电压表测量的是外电压,则A选项错误;电动势是将其它形式能转化为电能本领的物理量,电动势越大,将其它形式能转化为电能的本领越强,B选项正确;电路接通后电源两端电压是外电压,外电压小于电动势,C选项正确;电动势是由电源本身性质决定,与其它因素无关,则D选项正确。

阅读理解

阅读理解。

Dear Editor,

     I'm confused these days. We are taught at home and at school that violence (暴力) is bad. For example,

last week, my friend and I were playing at the beach. We found a really beautiful shell. My friend picked it up,

but I saw it first, and I said it was mine. He said, no, it was his. I really want the shell, and I even thought

about hitting him, that's how angry I was.

     Now should that be right? No! I shouldn't use violence. I should talk with my friend instead, and solve

that. My parents and teachers often tell me that using violence is the least civilized (文明)way to solve

problems.

     So, if adults had a disagreement, and if they used violence toward each other in order to win, is it all

right? No!

     Now, I'm confused. When two countries disagree, they often use violence. They fight a war. Using

violence is not okey at home, at school, or in your country but okey between two countries, why?

     A war is extreme violence. So not only soldiers but citizens (公民), including small children and babies

have been killed and injured because of wars.

     Adults say they are fighting wars in order to solve problems and make peace.But can you really "make

peace" by using violence and killing so many people?

     I don't think that bombs and missiles (炸弹和导弹) can reach people's hearts and change them. Bombs

and missiles can't create love and caring,and that's what we need in the world. Why can't they use their

wisdom (智慧) and talk it over?

1. What happened to Joshua and his friend last week at the beach?

A. They had a fight.

B. Joshua hit his friend.

C. They had a class about violence.

D. They found a beautiful shell

2. How should we solve problems according to this letter?

A. We should argue about the problems

B. We should study at school.

C. We should use our wisdom and talk them over.

D. We should use violence.

3. Which opinion is mentioned in the letter?

A. Violence can solve the problems.

B. We should fight wars.

C. A war is extreme violence.

D. Bombs and missiles can reach people's hearts.

4. What does the sentence "Bombs and missiles can't create love and caring, and that's what

    we need in the world." mean?

A. We need to use violence to solve problems.

B. What we need is bombs and missiles.

C. We need bombs and missiles to create love and caring.

D. What we need in the world is love and caring.

5. What's the letter about? It's about _______.

A. Joshua's thoughts about wars

B. Joshua's story

C. hate and love

D. arguments

单项选择题