Active Voice and Passive Voice Compared :  All the three Perfect Continuous Tenses and Future Continuous Tense have no passive voice.  So out of the 12 tense forms , only 8 have passive voice.  Some typical examples are given in order to clarify the structural differences of Active Voice and Passive Voice.  Once you study the examples carefully, you will become thorough with the grammatical rules behind.  The examples are given only for the purpose of teaching the grammar and usage and at times they may appear strange and practically not relevant.

• He eats a mango. Now see the passive voice – A mango is eaten by him.
• He eats two mangoes. —– Two  mangoes are eaten by him.
• He is eating a mango.—-  A mango is being eaten by him.
• He is eating two mangoes.—  Two mangoes are being eaten by him.
• He has eaten a mango.— A mango has been eaten by him.
• He has eaten five mangoes — Five mangoes have been eaten by him.
• He ate a mango. — A mango was eaten by him.
• He ate three mangoes —Three mangoes were eaten by him.
• He was eating a mango.—A mango was being eaten by him.
• He was eating three mangoes. — Three mangoes were being eaten by him.
• He had eaten three mangoes .—-Three mangoes had been eaten by him.
• He will eat a mango. —–A mango will be eaten by him.
• He will eat two mangoes. —Two mangoes will be eaten by him.
• He will have eaten a mango.  —- A mango will have been eaten by him.

Note :  Eminent grammarians do not appear to have used a ‘Passive Voice’ for verbs in Future continuous Tense.  However in recent times, a few books have come out with the argument that it would not be improper to derive a ‘Passive Voice’ for the verbs in Future Continuous Tense.  Anyway the disputed aspect has been excluded from this book with due respect to the acknowledged traditional scholars, but  of course not being disrespectful to the new ideas in this area.