1.  In an active sentence, the subject performs the action of the verb. An active sentence is the opposite of a passive sentence.  Examples:
  • The dog ate all the biscuits.

(In this example, The dog is the subject of the sentence. The dog is the subject of the verb to eat. The dog is performing the action of the verb; i.e., it is the thing doing the eating.)

Compare this to a passive version:

  • The biscuits were eaten by the dog.

(In this example, the biscuits did not perform the action of the verb. In fact, it was done to them. Therefore, this is a passive sentence.)

Examples of active sentences :

  • Tony is trimming the hedges all week.

(Tony is doing the action (trimming))

  • Hammerhead sharks will pester you as you approach the reef.

(Hammerhead sharks doing the action (pester))

In a passive sentence, the subject does not perform the action in the sentence. In fact, the action is performed on it.  For example    :

how to use passive in the sentence.

Example of passive sentences             :

Anita was driven to the theatre. (In this example, Anita did not perform the action of the verb to drive. The action was done to her. She was the recipient of the action.)

  • Nowadays, black kites are protected.

(The action is being done to the subject, black kites.)

  • The olives are stoned and crushed in this room.

(The action is being done to the subject, The olives.)

With a passive sentence, use By to show the actor     :

In a passive sentence, the person or thing doing the action (the actor) is usually preceded by the word by. For example:

  • Anita was driven to the theatre by Carla.
  • Nowadays, black kites are protected by law.
  • The olives are stoned and crushed in this room by my son.

The opposite of a passive sentence is an active sentence, in which the subject does perform the action of the verb.

2.  Characteristics of active and passive sentences are            :

  • Find the subject (the main character of the sentence).
  • Find the main verb (the action that the sentence identifies).
  • Examine the relationship between the subject and main verb.
    • Does the subject perform the action of the main verb? (If so, the sentence is active.)
    • Does the subject sit there while something else — named or unnamed —performs an action on it? (If so, the sentence is passive.)
    • Can’t tell? If the main verb is a linking verb (“is,” “was,” “are,” “seems (to be),” “becomes” etc.), then the verb functions like an equals sign; there is no action involved — it merely describes a state of being.

Basic examples                       :

I LOVE YOU.

  • The subject “I”
  • Action “Loving”
  • Relationship the subject (“I”) is the one performing the action (“loving”).

So, it is an active sentences.

YOU ARE LOVED BY ME

  • The subject “you”
  • Action “loving”
  • Relationship the subject (“You”) sits passively while the action (“loving”) is performed by somebody else (“me”).

So, it is a passive sentences.

3.   How to perform Active and Passive in several Tenses           :

Active                                     Passive

  • Past Tense                      I taught; I learned.                  I was (have been) taught                                                                                          by(someone).                                                                                                           It was (has been) learned by                                                                                      (someone).
  • Present Tense                 I teach; I learn.                        I am (being) taught by                                                                                               (someone).                                                                                                              It is (being) learned by                                                                                               (someone).
  • Present Continuous         Sarah is writing the letter         The letter (is being written)                                                                                       by Sarah.
  • Past Continuous              She was writing the novel         A novel (was being written)                                                                                       by her.
  • Present Perfect                Many tourists have visited         The castle (have been                                                the castle.                                visited) by many tourist.
  • Past Perfect                     George had repaired                  Many cars (had been                                                                                                  repaired) by George before                                                                                        he received his mechanic’s                                                                                        license.
  • With modals                    You must obey                          The traffic rules (must be)                                                                                          obeyed.
  • Intransitive verb             The earthquake happened          The earthquake (was                                                                                                happened) on March 11,                                                                                            2011 in Japan.
  • Transitive verb                The tsunami wave killed             Hundreds of people (were                                                                                          killed) the tsunami wave.

Sources              :

http://www.grammarbank.com/passives-with-modals.html

http://www.englishpage.com/verbpage/activepassive.html

http://www.englishpractice.com/improve/active-passive-voice-continuous-perfect-tense/

http://jerz.setonhill.edu/writing/grammar-and-syntax/active-and-passive-verbs/

http://www.grammar-monster.com/glossary/passive_sentences.htm

http://www.grammar-monster.com/glossary/active_sentences.htm