问题 名词解释

压电效应

答案

参考答案:

某些晶体在机械力作用下发生变形,使晶体内正负电荷中心相对位移而极化,致使晶体两端表面出现符号相反的束缚电荷,其电荷密度与应力成比例。这种由“压力”产生“电”的现象称为正压电效应。反之,如果具有压电效应的晶体置于外电场中,电场使晶体内部正负电荷中心位移,导致晶体产生形变。这种由“电”产生“机械形变”的现象称为逆压电效应。

阅读理解

阅读理解。

     Happiness is for everyone. You don't need to care about those who have beautiful houses with large

gardens and swimming pools or those who have nice cars and lots of money and so on. Why? .Because

those who have big house may often feel lonely and those who have cars may want to walk on the country roads at their free time.

     In fact, happiness is always around you if you put your heart into it. When you are in trouble at school, your friends will help you; when you study hard at your lessons, your parents are always taking good care of your life and your health; when you get success, your friends will say congratulations to you; when you

do something good to others, you will feel happy, too.All these are your happiness. If you notice them, you can see that happiness is always around you.

     Happiness is not the same as money.It is a feeling of your heart. When you are poor, you can also say

you are very happy, because you have something else that can't be bought with money. When you meet

with difficulties, you can say loudly you are very happy, because you have bad luck. As the saying goes,

life is like a revolving(旋转) door. When it closes, it also opens.  If you take every chance you get,  you

can be a happy and lucky person.

1. Happiness is for.

A. those who have large and beautiful houses

B. those who have cars

C. those who have lots of money

D. all people

2. When you do something wrong, .

A. people around you will help you

B. you will have no chance to challenge yourself

C. your classmates will laugh at you

D. you will be happy

3. Which is TRUE according to the passage?

A. When you get success, your friends will be very proud of you.

B. You can get help from others when you make mistakes.

C. You can still be a happy person even if you have little money.

D. All of the above.

4.We say "Happiness is not the same as money." because .

A. money always brings happiness

B. money doesn't always bring happiness

C. everything can be bought with money

D. only rich doesn't always bring happiness

5. Which is the best title of the passage?

A. Happiness.

B. Happy and Lucky.

C. Do Something Good to Others.

D. Life and Success.

单项选择题