问题 名词解释 简答题

相序

答案

参考答案:相位的顺序,交流电的瞬时值从负值向正值变化经过零值的依次顺序。电力系统中分ABC三相正常情况下三相电压电流对称,相位相差120O,但系统出现故障时,三相不再对称可将电压电流分解为正序、负序和零序三种分量。相序对电动机的旋转方向有影响。

阅读理解

阅读理解。

         If there is a fire disaster, knowing what to do is important. If a fire breaks out and runs into your

home, what should you do?

         First, you should keep calm and warn everyone in the house about the danger. Don't panic (be scared)

and start screaming. You can't take elevator to get down if you live in a high building. You'd better take stairs

with a wet towel. It is most important to be calm and act fast.

         Second, you and all the other people should get out of the house as quickly as you can. Don't stop to

take your belongings (物品) with you, even if there you have many valuable things in the house. And once

you are out of the house, stay out. Do not go back into the house for any reason.

          Finally, when you get out of the firing house, call 119 and let the skilled firefighters to put the fire out

at once. Don't try to put out the fire by yourself. That can be very dangerous.

1. What is the first thing you'd better do if a fire breaks out on your house?

A. Take out your belongings at once.

B. Start screaming at once.

C. Get down by taking elevator.

D. Warn everyone in the house.

2. What should you do once you are out of the house?

A. Panic.

B. Go back for the belongings.

C. Make a call.

D. Scream.

3. How should you get out of your home if you live in a high building?

A. You can take an elevator as quickly as possible.

B. You should get down on the stairs with something wet.

C. You'd better jump down through the window.

D. You can roll down from the window with a basket.

4. You should call the firefighters .

A. after you leave the house

B. after you take your belongings

C. when you are trying to put out the fire

D. before you warn everyone

5. What does the passage tell us?

A. Don't be afraid before leaving the house.

B. Don't put out the fire by yourself.

C. It's better to let your belongings burn.

D. Obey some important rules if you meet a fire.

单项选择题