过去式的被动语态什么时候用

当时态是一般过去时，语态是被动语态时，要用过去式的被动语态。

一般过去时的被动语态时构成是：

助动词was/were+及物动词的过去分词

例句：

1、I sweep the floor yestetday.

→The floor was swept (by me) yestetday.

2、I bought a book last week.

→A book was bought (by me ) last week.

3、We visited their school yeaterday.

→Their school was visited (by us) yesterday.

主语是动作的接受者，一般为物，表达“某事被人做”，而且是过去被人做的时候，用过去式的被动语态。比如: The book was published last month. 这本书是上个月出版的。