Words in a sentence can be arranged rearranged in any way grammatically correct to form a sensible statement. However this arrangement of words is what can make a lot of the difference given the meaning, one important point to be kept in mind is that the meaning of these sentences should remain intact when one changes from active voice to passive voice and vice versa.
A sentence is made up of two essential components, a subject and a verb. The subject is an agent and the doer of the action, the verb.
Take a closer look at the sentence below
He loves fish tacos.
He is the subject, loves is the verb and fish tacos is the object.
I wrote a letter
I is the subject, wrote is the verb and letter is the object.
Active voice is called so because the subject acts directly on the object.
Therefore, the verb is in the Active voice when the person of the thing denoted by the Subject is the doer of the action.
Passive voice when the object is acted upon by the subject. It is called so because the person or thing denoted as the Subject is not active but passive and that it receives some action.
Eg : Fish tacos are loved by him.
A letter was written by me.
We can notice that when a sentence changes from Active to Passive voice, the object of the transitive verb in the active voice become the subject of the verb in the passive voice.
( Fish tacos which is the object of loves in active voice becomes the subject of are loved in the passive voice.
Similarly, A letter which is the object of write in the active voice becomes the subject of was written in the passive voice.)
:- Note only transitive verbs can be used in Passive voice and since the object of the verb is in the active voice, it becomes the subject of the passive form.
:- An intransitive verb has no object
Active voice : The horse kicked the man.
Passive voice : The man was kicked by the horse.
Active voice : The Hungry lion roars.
Passive voice : Not possible because there is no object.
:- The passive voice is formed with the suitable tense of the be verb followed by the past participle.
Conversion from Active voice to Passive voice and vice versa alone is not sufficient. We must also know when to use them efficiently in appropriate places.
Active voice is used when the agent acquires prominence, while Passive voice is used when the person or object acted upon acquires prominence. Thus, Passive voice is generally preferred when the agent involves the use of indefinite pronouns (somebody, they, people.. as subject) since the agent is unknown or not clear.
I have been invited to the party
(Someone has invited me to the party)
All orders will be executed promptly
(We will execute all orders promptly)
The agent by is usually avoided in such cases.
:-However, in the earlier examples the usage of by is quite inevitable as it has some importance and therefore it will make complete sense only when it is used.
:- When changing from Active voice to Passive voice, if the verbs take both direct and indirect object, either object may become the subject of the Passive voice while the other is retained.
Eg: The teacher will give you a hand book.
A handbook will be given to you by the teacher.
:- An indirect object denotes the person to whom or for whom something is given or done, while a direct object usually denotes a thing. In such cases, it is probably more usual for passive constructions to begin with the person.