问题 单项选择题

交流电的功率因数等于()。

A.瞬时功率与视在功率之比

B.电路的无功功率与有功功率之比

C.电路的电压与电流相位差的余弦

D.电路的电压与电流相位差的正弦

答案

参考答案:C

多项选择题
阅读理解

阅读理解

     One day an Australian farmer, Joe, saw a bright light in the sky.①The light came nearer and nearer and suddenly

Joe saw that it was a spaceship. The spaceship landed in a field quickly.    The door of the spaceship opened and two

strange beings climbed out.②They seemed to be half man and half bird. Joe was afraid of them. He tried to run away.

But the spacemen walked towards him, picked him up and carried him into the spaceship. They put wires(电线) from

a machine onto his head and they could speak to him in English.

     They asked him some questions about the earth. "We are from Venus," they said, "but it's getting very hot there. A

lot of our people are dying and we don't have much time left. We are trying to find a new home."

     After some time they③freed Joe and at last the spaceship took off and could not be seen again. Joe told his friends

about the spaceship, but no one believed his story.

     "You'll believe me one day," Joe told them. "The spaceman will come back..."

1. 翻译①处画线部分句子

    _______________________________.

2. 不改变句意,改写②处句子

    _______________________________.

3. According to the conversation between Joe and the aliens, what do we know about Venus?

    _______________________________.

4. ③处单词的意思是_____

A. let…go

B. paid no money

C. took away

D. locked

5. 用文中的两个词填空。

    (1) Some people _____ in everlasting life after death.

    (2)The girls are _____ of going out at night.