Simple Passive

Use:       

The passive voice is used:
a) When the object of a sentence is more important than the subject
The city was destroyed by the volcano.

b) When the subject of the sentence is unknown.
This cheese was made in Canada.

 It is common in formal and scientific writing.

Form:
You can use the passive voice in all tenses. Use the correct form of be + the past participle of the verb.

Present Simple: I  you / they / we It / She / he	am are is	Past participle taken given built made eaten brought cooked left...	The workers collect the rubbish of Wednesdays. =>  The rubbish is collected on Thursdays.
Past Simple: you / they / we I / It / She / he	were  was		People built the castle over 800 years ago. =>  The castle was built over 800 years ago.
Present Perfect: I / you / they / we It / She / he	have been has been		Someone has taken my book! =>  My book has been taken!
Past Perfect: I / you / they / we / it / she / he	had been		When we arrived at the airport, someone had resold our tickets. =>  When we arrived at the airport, our tickets had been resold.
Modals I / you / they / we / it / she / he	can be will be would be must be should be could be		You must wear a hard hat in this area. =>  Hard harts must be worn in this area.

To mention who caused the action, use by.
The bins were emptied by the cleaning staff.