一、被动语态的构成。
被动语态的形式是由“助动词be+动词的过去分词”构成。助动词be随着主语的人称，数，时态和语气的不同而变化。各种时态的被动语态形式如下：
1.一般现在时am/is/are+V，
人们利用电能运转机器。
People use electricity to run machines.
Electricity is used to run machines.
Is electricity used to run machines?
Yes, it is . / No, it isn't.
2.一般过去时was/were + V
昨天我们在山坡上种了许多树。
Many trees were planted on the hill yesterday.
3.一般将来时will/shall +be+V 下星期我们将举行一场运动会。
A sports meeting will be held next week.
4.过去将来时should/would +be+V
他告诉我们人们将在他家乡建一个大水坝。
We were told that a big reservoir would be built in his hometown.
5.现在进行时am/is/are +being+V
他正在油漆房子。
He is painting the house.
A house is being painted.
Is the house being painted?
Yes, it is. / No, it isn't .
6.过去进行时was/were +being+V
当我进厨房时，她正在做蛋糕。
A cake was being made when I came into the kitchen.
7.现在完成时have/has +been+V
他已经结束工作了。
He has finished his work.
His work has been finished.
8.过去完成时had +been+V
到上个月为止，他们已经把这本书翻译成了英语。
The book had been translated into English by the end of last month.
9.将来完成时will have +been+V
2,000 words will have been learned by the end of next year.
注：
1. 含有情态动词的谓语变成被动语态时，用“情态动词+be+V”构成。
如：The machine must be operated with care.
2.含有"be going to"，"be to"等结构的谓语，变成被动语态时，分别用"be going to +be +V"和“be to +be+V”。
如： The problem is going to be discussed at the meeting.
二、由动词短语形成的被动语态： 一般情况下，只有及物动词才能跟宾语，
而不及物动词不能跟宾语，所以只有及物动词才有被动语态，不及物动词则没有被动语态。
但有些不及物动词后面跟上介词或副词后，变成一个动词短语，相当于一个及物动词，就可以形成被动语态。
约翰打开了收音机。
John turned on the radio. The radio was turned on.
奶奶照看我姐姐。
Grandma takes care of my sister. My sister is taken care of by Grandma.
注：千万不要遗漏介词或副词。
难点释疑：
主动形式表被动意义。在下列情况中，谓语形式是主动的，但具有被动的含义。
The food tastes delicious.
这种食物尝起来很可口。
The idea sounds good.
这个主意听起来不错。
The apples sell well.
这些苹果很好卖。
The clothes wash well.
这些衣服很好洗。
一些固定句型表示被动含义。
a. be worth doing sth The film is well worth seeing.
这部电影很值得一看。
b. have/ get sb/sth done have作使役动词没有被动语态，但可用这种结构表被动或使役。
I had my watch stolen.
我的手表被偷了。
c. sth need/want/require doing=sth need /want/require to be done The room needs cleaning.
=The room needs to be cleaned.
这间房屋需要打扫。