Active voice is more direct than passive voice because of the simple, easily digestible subject-verb format. In an active voice, the subject does an action. For example, "Betty eats cake." Betty is clearly doing the action here (eating cake), and the object in active voice is the cake. Active voice also tends to make for shorter, more palpable writing, both in narrative writing and any other kind of writing, since it is so simple and straight to the point.
Critics and writers generally give passive voice a bad rap in most cases, since the format of passive voice makes the sentence less direct and more clumsy and wordy. In passive voice, the subject of the sentence is acted upon, as opposed to committing the act. From the example shown above, "Betty eats cake" would in passive voice be "The cake was eaten by Betty." With this change, the focus shifts to the cake instead of Betty.
At times it may be difficult for some writers to tell whether or not they are writing in passive or active voice. One rule to go by is, in passive voice, the subject does not take direct action. To change your sentence from passive to active, first make the original object the subject. Then omit the "to be" form and the past tense verbs ("was eaten," "to be acted"). Finally, turn the original subject into the direct object. Therefore, a passive sentence such as "Greg is liked by Corey" turns into the active "Corey likes Greg."
Although use of passive voice is commonly discouraged in writing, it does have some uses. It can be used if the person taking the action is unknown or needs to be obscured. Passive voice is used commonly in news stories, with phrases such as "the store was robbed," "the bombs were dropped," or "Cindy was mugged." Passive is also used in crime reports when the culprit of a crime is unknown. In narrative fiction, passive voice can help you focus on an unknown person committing certain acts, such as "the vase was broken," or "somebody killed Mr. Body." Scientists are encouraged to write in passive voice, as it lends a sense of objectivity and takes the focus away from the scientists themselves who performed the experiments.