一、被动语态的用法：
1、不知道或没有必要指出谁是动作的执行者时。
The bridge was built last year.这座桥是去年建造的。
He was elected chairman.他被选为主席。
2、当更加强调动作的承受者时。此时动作的执行者由by引导置于谓语动词之后，不需要时可以省略。
The room hasn't been cleaned yet.房间还没有打扫。
The tiger was killed by him.老虎被他杀死了。
3、当动作的执行者不是人时，多用被动语态。如：
The window was blown by wind.窗户被风吹开了。
The whole village has been washed away by the flood.整个村庄都被洪水冲走了。
4、表示客观的说明常用"It is + 过去分词."句型。
It is said that Lucy has gone abroad.据说露茜已经出国了。
It is believed that he is a spy. (=He is believed to be a spy.)大家相信他是个间谍。
其它常见的"It is + 过去分词+ that"句型还有
It is reported that…据报道
It is said that…据说
It is believed that…大家相信
It is suggested that…有人建议
二、主动语态变为被动语态
1、主动语态变为被动语态的步骤：
（1）将主动句的宾语变为主语：
注意：如果主动句的宾语是代词，需将其由宾格变为主格。如：
Tom killed him. → He was killed by Tom.
（2）将动词改为"be+过去分词"。
注意：
They held a meeting yesterday. → A meeting was held by them yesterday.
他们昨天开会了。
（3）将主动语态的主语改为be…放在谓语动词后。
注意：如果原主语是代词，则应由主格变为宾格。
He sang a song. → A song was sung by him.
2、主动语态变为被动语态的注意事项：
（1）主动句中的主语如果是people, we, you, they, somebody等含糊地表示"人们"、"大家"的单词，变为主动句时，通常删去"by…"，但原主语被强调者除外。如：
They set up this hospital in 1975. → This hospital was set up in 1975.
这所医院建于1975年。
Only he can finish the job. → 只有他能完成这项工作。
The job can be finished only by him.这项工作只能由他来完成。
（2）含有双宾语，即直接宾语和间接宾语的句子，每个宾语都可变为被动语态的主语，即其被动语态有两种形式。但多以间接宾语作主语。
Jack told us the truth.杰克告诉了我们真相。
We were told the truth by Jack.
The truth was told (to) us by Jack.
三、动词的主动形式表示被动之意
以主动形式表示被动之意的动词多为连系动词，如：look, feel, smell等。下列动词没有被动式：happen，cost，take，have
An accident was happened yesterday.（×）昨天发生了一起事故。
An accident happened yesterday.（）
The flower smells sweet.这花闻起来很香。
The watch looks good.这表看起来很好。
This book sells well.这本书畅销。
四、各种时态的被动语态举例（以动词do为例）
1．一般现在时（am/ is/ are +done）
English is spoken by lots of people in the world. 世界上的许多人都说英语。Class meeting is held every Thursday. 每周四都举行班会。
The classroom is cleaned by the students every day. 学生们每天都打扫教室。2．一般过去时(was/ were +done)
The cup was broken by the boy. 杯子被那个男孩打碎了。
He was saved at last. 他最终获救了。
My bike was stolen. 我的自行车被偷了。
3．一般将来时与过去将来时(will/ shall be +done; would/should be +done)
A speech will be given this afternoon. 今天下午有一个演讲。
A new road will be built next year. 明年要修一条新马路。
I thought thousands of people would be helped. 我认为将有数千人得到帮助。4．现在进行时与过去进行时(am/ is/ are being +done; was/ were being +done) The machine was being repaired at this time yesterday. 昨天这时，机器正在被修理。
The problem is being discussed now. 问题正在被讨论。
A bus is being pushed by the passengers. 路人正在推一辆公共汽车。
5．现在完成时(have/ has been + done)
Two hundred trees have been planted by now. 到现在为止，已经种了二百棵树了。
The book has been read many times by me. 这本书已经被我读了许多遍了。
