Present simple and continuous: The car is repaired. The car is being repaired.
Past simple and continuous: The car was repaired. The car was being repaired.
Present perfect: The car has just been repaired.
Past perfect: The car had been repaired.
Future simple: The car will be repaired.
Future perfect: The car will have been repaired.
Present and perfect conditional: The car would be repaired. The car would have been repaired.
The passive voice in English is formed with the verb to be and the past participle, which is different for regular verbs (translated, mended) and irregular verbs (taken, thrown).
Statement: The letter is written. This shop has been opened. It will be done in time.
Question: Is the letter written? Has the shop been opened? Will it be done in time?
Negative: The letter is not written. The shop has not been opened. It will not be done in time.
The continuous is as follows. (Other continuous tenses are normally used in the active voice, not in the passive.)
Present: A new house is being built in our street.
Past: A new house was being built in our street.
In all the examples above the agent is not mentioned. We do not know who has written the letter or opened the shop.
Similarly: Flowers were planted in the garden. (We do not know who did it).
If we want to say who planted the flowers we mention the agent at the end of the sentence and use the preposition by.
The flowers were planted by my mother.
But: The window was smashed with a stone. (The stone is not the agent. We do not know who smashed the window. We only know how he or she did it).
Direct and indirect objects
If there are both direct and indirect objects in the active voice (My friend sent me a letter), the indirect object (my friend), not the direct object (a letter), becomes the subject in the passive voice.
Active: My friend sent me a letter.
Passive: I was sent a letter by my friend. (Not: A letter was sent to me by my friend. This sentence does not sound natural in English.)
Similarly: They offer Trevor a place. - Trevor is offered a place.
The infinitive without to
In the active voice some verbs are followed by the bare infinitive (infinitive without to). In the passive form we use most such verbs with the infinitive with to.
Active: We saw them come. She made him do it.
Passive: They were seen to come. He was made to do it.
But: They let us go. - We were let go.
The passive is used:
1. If the action is more important then the agent.
A demonstration has been held. This theatre was built in 1868.
The important thing is what happened, not who did it.
2. If the agent is not known.
He was offered a job. (Someone offered him the job.)
They are supposed to be good students. (Some teachers suppose that.)
The difference in meaning between the simple and continuous
A new house is built in our street. (The house is finished.)
A new house is being built in our street. (They are building it these days, it is not finished.)
I was being introduced to Mrs. Jones when her husband arrived. (Her husband arrived in the middle of the introduction.)
When her husband arrived I was introduced to Mrs. Jones. (Her husband arrived first and then she introduced me.)
This form is typical of an impersonal and formal style, that is why you can often find it in public notices, announcements, instructions or scientific articles.
English is spoken in this shop. Visitors are not allowed to smoke. The seal must be removed.
In a less formal style the active voice is more usual.
English is spoken in this shop. - We speak English in this shop.
He was seen in Dover. - They saw him in Dover.
The seal must be removed. - You must remove the seal.
In the English language this form is more frequent than in many other languages. Moreover, you can find some stuctures in English which are not possible in some languages.
I am told that you are going to have a baby. It is thought that the crises will end soon.