Active voice and passive voice

Active voice is the voice of spoken person; this voice is about what he spoke. Passive voice is the voice when we say the voice of that spoken person in our own words.
Simple pattern of passive voice is
Object + helping verb + third form of verb + object
Following are the examples which can help in solving the problem of active voice and passive voice.
Active voice: He writes a letter.
Passive voice: A letter is written by him
Active voice: I eat apples.
Passive voice: Apples are eaten by me.
From above example it is clear that in passive voice work is done with force.