问题 问答题 简答题

焊接时产生电弧和维持电弧燃烧的必要条件是什么?

答案

参考答案:

1)焊接电源,焊接电源的特性符合电弧燃烧的要求,则电弧稳定燃烧;2)焊接电流种类,交流电源焊接时没有直流电流稳定;3)焊接电源的空载电压,具有较高空载电压的焊接电源不仅引弧容易,而且电弧燃烧稳定。

阅读理解

阅读理解。

     Mrs Jones was still cleaning the house when her husband came back from work. She was wearing

dirty, old clothes and mo stockings (长袜) and her hair was not tidy. She looked dirty and tired. Her

husband looked at her and said, " Is this what I come home to see after a hard day's work?"

     Mr Jone's  neighbour, Mrs Smith, was there. When she heard Mr Jone's words, she quickly said

goodbye and ran back to her house. Then she washed and combed (梳理) her hair carefully, put on her

best dress and her most beautiful stockings, painted her face, and waited for her husband to come home.

     When he arrived, he was tired. He walked slowly into the house, saw his wife and stopped. Then he

shouted (大喊) angrily, "And where are you going this evening ?"

1. What was Mrs Jones doing, when her husband came back from work?

A. She was cleaning the house.          

B. She was making some cakes .

C. She was putting on her old clothes.  

D. She was talking off her stockings.

2. What did Mr Jones feel when he saw his wife?

A. He felt very happy.              

B. He felt nothing.

C. He was pleased to see his wife.  

D. He felt unhappy.

3. Why did Mrs Smith run back quickly to her house when she heard Mr Jone's words?

A. She was afraid of Mr Jones.

B. She didn't like Mr Jones , so she didn't want to see him any more.

C. She thought she should do something before her husband went back.

D. She wanted to watch TV.

4. What did Mr Smith think when he saw his wife?

A. He thought his wife was beautiful.

B. He thought his wife was waiting for him.

C. He thought his wife was ugly (丑的).

D. He thought his wife would go out that evening. 

5. Did Mr Jones really love his wife?

A. No, he didn't.                  

B. Yes, he did.

C. No, but Mr Smith loved his wife.

D. Yes, he loved his wife very much.

单项选择题 A1/A2型题