The sentence structure in English ALWAYS requires that the sentence begins with the subject followed by the verb and the object.
The same happens in passive sentences in which the object of an active sentence becomes the subject; in either case it receives the action of the verb.

A passive sentence is formed by conjugating the verb TO BE, which is the same as that of the active sentence, and is followed by the past participle of the main verb.
Moreover, the agent in the passive sentence (person or thing performing the action – the subject in the active sentence) usually isn’t mentioned, however when it is, it’s introduced by the preposition BY.
On the other hand to ask who has performed the action “by” will be positioned at the end of the question:
– Who was this written by?
The same happens with other prepositions:
– What was the woman killed with?
– Who will the letter be mailed to?
The following table shows the different conjugations of the verb TO BE in the various verb tenses

HOW AND WHEN WE USE THE PASSIVE VOICE
1. When it’s more important to describe an action or event than knowing who performed the action:
– The tyre was patented in Great Britain in 1888/89;
2. When the person or thing performing the action is unknown:
– The Museum of Modern Art in our city was renovated two years ago;
3. for notices, communications, announcements, newspaper articles or to describe scientific processes:
– Smokers will be fined on the spot
– The liquid was filtered and…
– An agreement has been found between the government and the Trade Unions;
4. to translate the Italian impersonal form introduced by “si” (si parla, si vende, si fabbrica…):
– English is spoken here
– Stamps are sold here
– Fine silk ties are made in Como

It is also possible to use the passive sentence with Modal Verbs and with “Have to”, they must be followed by a passive infinitive:

© L. R. Capuana