Saylor.org's English Composition/Active versus Passive Voice
Although grammatically correct, passive voice is a form of writing that often comes across as clunky or stylistically ugly by many academics or professional writers. One might be tempted to confuse passive voice with past tense. However, as the examples will show, past tense can be written in an active voice and in a manner that makes the writing much stronger. The construction of a passive voice sentence in English takes the following form: Auxiliary verb (be or get) + participle of transitive verb
Examples: The ball was hit by John. These books were read by the students. My pet dogs got fed by my mom.
Although the transitive verb is often followed with the word 'by' to indicate who performed the action, it is not always necessary. For example, the sentences "the ball was hit," "these books were read," and "my pet dogs get fed" are all grammatically correct.
So, what does active voice look like and how can those sentences be re-written in active voice?
John hit the ball. The students read these books. My mom fed my pet dogs.
Not only are these sentences cleaner, they avoid the repetitive use of 'to be' verbs (by its very definition, a very stagnant and uninteresting verb). Keep in mind, that present tense can be written with passive voice as well.
Passive: You are interested to learn about passive voice. Active: Learning about passive voice interests you.