Voice change is the process of changing the form of a verb to indicate whether the subject is the doer or the receiver of the action. Voice change can be done from active voice to passive voice, or vice versa. Here are some general rules for voice change:

• The object of the verb in the active voice becomes the subject of the verb in the passive voice, and vice versa.
• The verb in the active voice is changed into the past participle form, and the verb ‘to be’ is added before it. The verb ‘to be’ should agree with the subject in number and person, and should have the same tense as the verb in the active voice.
• The subject of the verb in the active voice becomes the agent or doer of the action in the passive voice, and is usually preceded by the preposition ‘by’. The agent can be omitted if it is not important or obvious.
• The structure of the sentence should not change. If the sentence is affirmative, negative, interrogative, or imperative, it should remain so after voice change.

Here are some examples of voice change for different tenses:

Present simple tense

• Active: He writes a letter.
• Passive: A letter is written by him.

Present continuous tense

• Active: She is singing a song.
• Passive: A song is being sung by her.

Present perfect tense

• Active: They have finished their homework.
• Passive: Their homework has been finished by them.

Past simple tense

• Active: He broke the window.
• Passive: The window was broken by him.

Past continuous tense

• Active: She was painting a picture.
• Passive: A picture was being painted by her.

Past perfect tense

• Active: They had completed their project.
• Passive: Their project had been completed by them.

Future simple tense

• Active: He will buy a car.
• Passive: A car will be bought by him.

Future perfect tense

• Active: She will have cooked dinner.
• Passive: Dinner will have been cooked by her.

For more information and examples on voice change, you can check out these web search results¹²³⁴⁵. I hope this helps you understand voice change better. 😊

The formula for each tense is a way of expressing how to form the verb in that tense. Here are the formulas for 12 common tenses in English:

• Present simple tense: Subject + base form of verb (+ s/es for third person singular)
• Past simple tense: Subject + past tense form of verb
• Future simple tense: Subject + will + base form of verb
• Present continuous tense: Subject + be (is/am/are) + verb + ing
• Past continuous tense: Subject + be (was/were) + verb + ing
• Future continuous tense: Subject + will be + verb + ing
• Present perfect tense: Subject + have (has/have) + past participle form of verb
• Past perfect tense: Subject + had + past participle form of verb
• Future perfect tense: Subject + will have + past participle form of verb
• Present perfect continuous tense: Subject + have (has/have) been + verb + ing
• Past perfect continuous tense: Subject + had been + verb + ing
• Future perfect continuous tense: Subject + will have been + verb + ing

For more details and examples, you can check out these web search results¹²³⁴. I hope this helps you learn the formulas for each tense. 😊

Source:
(1) Tense Chart: with Rules Examples & Formula – OnlyMyEnglish.
(2) 12 types of Tenses with Examples and Formula – MyEnglishTeacher.eu.
(3) 12 Tenses Formula With Example PDF – English Grammar Here.
(4) All Tenses with Formulas | Present, Past, Future Tenses – Englishan.
(5) Voice Change in English Grammar – Rules | Example | Exercise – Examyear.
(6) Voice Change Rules: Active to Passive Voice with Examples.
(7) Voices English Grammar: Active Voice & Passive Voice in Each Tense with ….
(8) The change of voice from active to passive and vice-versa – Unacademy.
(9) Active Voice and Passive Voice – KVS.