Active voice constructions offer a clear relationship between subject and an action. Active sentences typically employ strong phrase constructions that combine a clear subject with a precise verb. Writers should use the active voice to avoid wordy or confusing sentences that frequently occur when a writer employs the passive voice.
A sentence constructed in the active voice has a subject that performs a specific action. For example, "David earned a B in his science class". The passive voice creates sentences in which the subject receives an action, which in this case would be, "David was given a B in his science class." In many instances the passive voice will create a wordier and less direct sentence construction.
When you are trying to change sentences to the active voice you must first identify the subject and verb, and ensure that the subject is performing the action. In some cases formal writing can use the passive voice to leave the subject of the sentence anonymous. For example, "It was proven that smoking causes cancer." In this case use a general term such as "research" or "studies" as the subject of the sentence, and create a sentence such as, "Research proves that smoking causes cancer."
Beginning writers should practice the passive voice and learn to create clear, precise sentences before they begin to develop more complex sentences with the passive voice. Some fields of study tend to employ the passive voice more frequently to create a more authoritative tone or emphasize the action rather than the actor. Writers in these fields will have to learn to use the passive voice in a clear, concise manner in order to avoid wordy or confusing content.