English lesson_passive form of verbs

The passive form of verbs is formed of BE + the past participle,
(example : English is spoken here)

◊ We use the active form of a verb to say what a subject does.
Example : The chef cooks food every day.

◊ We use the passive form to say what happens to the subject.
Example : Food is cooked every day.

                                          ◊   The subject of a passive verb corresponds to the object of an active verb.
                                                 *Food is cooked every day. (Passive)
                                                 *The chef cooks food every day. (Active)

                                          ◊   We use the passive form of a verb when it is not important who does the action,
                                               or when we don't know who does it.

*The letter was delivered at 9 a.m.
(The identity of the person who delivered the letter is unknown or unimportant.)

If we want to say who does the action, we use 'by' :
*The letter was delivered by the postman.

VERB	ACTIVE	PASSIVE
Infinitive	To cook	To be cooked
Present Simple :	I cook food in the kitchen.	Food is cooked in the kitchen.
Present Continuous :	I am cooking food in the kitchen.	Food is being cooked in the kitchen.
Present Perfect :	I have cooked food in the kitchen.	Food has been cooked in the kitchen.
Past Simple :	I cooked food in the kitchen yesterday.	Food was cooked in the kitchen yesterday.
Past Continuous :	I was cooking food in the kitchen.	Food was being cooked in the kitchen.
Past Perfect :	I had cooked food in the kitchen.	Food had been cooked in the kitchen.
Future Simple :	I will cook food in the kitchen.	Food will be cooked in the kitchen.
Future Perfect :	I will have cooked food in the kitchen.	Food will have been cooked in the kitchen.