Theory:

Passive Voice:
The passive voice is used when we want to emphasize the action (the verb) and the object of a sentence rather than subject. This means that the subject is either less important than the action itself or that we do not know who or what the subject is.
 
We form the passive with the verb to be and the past participle of the main verb.
Example:
The questions were solved by the teacher.
Here the question is the object and teacher is the subject as the subject is acting upon the object (question). The action of the teacher(subject) is directed towards the object (question).
 
1. We form positive sentences by putting the verb form in the second place:
 
SUBJECT \(+\) TO BE \(+\) PAST PARTICIPLE
 
2. We form questions by putting the verb to be before the subject.
3. We form negative sentences by putting not after to have or to be.
 
Active Voice:
In an active voice, the sentence has a subject acting on its verb. Here the subject is emphasized more than the object.
Example:
The teacher was solving the questions.
Here the importance is given to the subject (Teacher), rather than the question(object). The sentence is about what the teacher was doing.
 
Some sentences with active voice from the lesson "From Zero to Infinity":
  • The teacher was solving questions on division.
  • Three bananas were drawn on the blackboard.
  • A smart boy in the front row replied.
  • A boy sitting in one corner raised his hand.
  • The teacher thumped the desk.
  • The boys understood the trick.
  • Senior students clarified their doubts with him.
  • He put forth many mathematical formulae.
  • He did all his problems on loose sheets of paper.
  • He mastered the difficult book
  • Ramanujan looked for a job.
Turning these sentences into passive voice, we get:
  • Questions on division were solved by the teacher.
  • The blackboard had three bananas drawn on it.
  • The reply was given by a smart boy in the front row.
  • The hand was raised by a boy sitting in the front row.
  • The desk was thumped by the teacher.
  • The trick was understood by the boys.
  • Doubts were cleared by senior students with Ramanujan.
  • Many mathematical formulae were solved by him.
  • Problems were solved by him on loose sheets of paper.
  • The difficult book was mastered by him.
  • A job was looked for by Ramanujan.