I bring back this thread from the old forum, just as GrumpyElf's suggested.

ACTIVE VOICE
Most of the times the idea of sentences in active voice is to focus on who does the action. The subject comes to be relevant for the situation.

As you can see, these are essential to understand the sentence.

Now, the idea of PASSIVE VOICE is to make the sentence impersonal. That is, when the subject of the sentence (which, as we'll see later, will simply become an agent and complement) is not as relevant as the one which/who has been affected by the action or even not as relevant as the action itself!

Who offered the aid, who is checking the baby or who will carry out the construction is either irrelevant or obvious. As a result, they're not mentioned in the sentence.

Now, let's see the structure.
The basic structure in ACTIVE VOICE is the Subject [1] (who does the action), the action [2] (conjugated verb) and the OBJECT [3], or the item or person that is affected by the action. It is essential to remember that, in order to have a sentence in Passive Voice, we must have a Transitive Verb (a verb with an object). Let's see these sentences in Active Voice. Which sentences can be transformed into Passive Voice?

It's those sentences with an object that can be converted into Passive Voice. Those sentences which have an adverb or adjective as a complement cannot!

OK, now let's work on the magical transformation from Active to Passive voice (in real life, however, more than transformations you'll just need to make sense of the structure!)

STEP 1) What was the object now becomes the subject. Let's use the very last sentence we used as an example:

Taxis is the object in the original sentence. Now it becomes the subject in the structure of our new sentence.

STEP 2) Identify the principal verb in your sentence. WHAT IS ITS TENSE? Present? Past? Future? Progressive? Simple? Perfect? Perfect Progressive? A modal verb? Based on it you're going to conjugate the VERB TO BE. Let's go back to our sentence:

The verb form is in Present Simple, so we're going to conjugate the verb TO BE in present simple.
WARNING: Don't rush while making Passive sentences. In many occasions, students make mistakes simply because of the conjugation of Passive Voice!

STEP 3) Conjugate the principal verb into its Past Participle, right after the verb TO BE. We can have either a regular or an irregular verb:

USE is a regular verb, so let's conjugate it into its past participle form.

STEP 4) Include the rest of the information for your sentence (complements) they can be adverbs of frequency, time, place, mode, etc. One of the most common cases is the agent, or who did the action. It is inserted as a complement because it is secondary information. Let's see something interesting in Passive Voice, though:

As far as I know, horses don't use taxis. In other words, the agent as a complement is unnecessary in many occasions because it is irrelevant or implicit! If you decide to use the agent, make sure you use the preposition BY.

OK, based on these magical steps, let's see the transformation from active to passive. Let's observe how we play with these elements:

Can you see how the order changes? The keys of Passive voice are:
1) Identifying the object
2) Conjugating the verb BE properly, and
3) Conjugate the principal verb in part participle.

The key number 2 is very important. As I said before, many students make mistakes while conjugating. For instance, I typically use the sentence My mother is preparing a birthday cake. When I ask my students to transform the sentence so as to make it systematic, they don't take enough time to conjugate the verb To Be the way it should be! So they ignore its tense is PRESENT PROGRESSIVE! Nicole, it's very different to say A birthday cake is prepared by my mother and A birthday cake is being prepared by my mother.
So take all your time to use the verb To BE correctly! Life's long enough!

Before advancing on the topic, I've got a number of sentences for you to transform from active to passive voice. Once this is solved, I'll show you the two possibilities for Passive Voice, and the Passive Causative in context!

OK, here we go:

1. Children read many adventure books nowadays.
2. The city council is editing the traffic agreement.
3. Users have not paid the fee.
4. People cannot take the books away from the library.
5. Someone broke the main door's glass.
6. The workers were re-decorating the house.
7. Michael had finished the essay.
8. People will re-elect the major.
9. They are going to construct a new bank.
10. They should renew the website.

Good luck with your challenge!

Spoiler:

As we said before, you use Passive Voice when you want to make an action impersonal, that is, when you don't want to emphasise on the person or thing that does the action, but on the action itself or on the one that is affected by such action.
Passive voice is commonly used in the news as well as in the description of processes, and in academic talk.


We said that an object is essential to have a passive form as it's the one which will become the subject in the sentence. Let's see these sentences:

As you can see, these sentences have two objects. One is the direct object, which is the person or thing directly affected by the action, the principal object. We also have the indirect object, which is also affected by the action but in an indirect way, it is involved in the situation. Many of the sentences given above have two versions of passive voice, depending on what you want to focus on. Do check the first example:


A lot of work is the direct object (That is what the boss gives). Me is the indirect object. So these are the two possible passive forms:

A lot of work was given to me. This is the typical Passive Voice form, as aforementioned. The Direct object becomes the subject, then you conjugate the verb BE and use the verb in past participle. The Indirect Object becomes a complement in the sentence.

I was given a lot of work The indirect object turns into a subject as you want to focus on it. Then, as a typical passive sentence, you conjugate the verb BE, the principal verb in Past Participle, and the direct object continues being the object.

Time to check another sentence:


Lots of wonderful presents is the Direct Object, whereas HER is the [i]Indirect Object. So these are the alternatives:
Lots of wonderful presents are being given to her. You focus in what is being given to her,
or
She's being given lots of wonderful presents. You focus on who is being given the presents.

Can you transform these sentences?

1. They told lies to me.
2. John will send Jane beautiful flowers.
3. They have written a letter to my lawyer.
4. I am going to dedicate this sing to my mother.
5. I can show your friend the new computer.
6. Maggie left her son a lot of money.
7. The teacher has given us homework.
8. My sister sold her car to Alex.

Later on: Passive Causative and Passive Voice in reported speech.

Hi!

These are some links to practice Passive voice and its conversion from/to active voice.

• English4Fun! Exercise - Active - Passive Switch.
  
• English Hilfen - Lots of exercises for Passive Voice.
  
• EnglishGrammar.org - More exercises.
  
• English Grammar Online 4 U - More and More exercises

Enjoy!!
Don't forget to report your results and ask any question you've got!

Thank you for the post for exercises. I will be waiting for passive causative and reported speech with passive voice.