Using the active voice makes your writing simple, clear, concise and immediate, drawing your reader into the action of the piece and giving your writing energy. Using passive voice, on the other hand, can make your writing seem too formal, dull and wordy and can create a distance between the reader and the words.
Passive
In passive sentences, the thing acted upon is the subject of the sentence, and the thing doing the action is usually included at the end of the sentence, for example:
The book was read by Sam.
The book is the subject receiving the action, ‘was read’ is the passive verb and Sam is doing the action.
Active
In active sentences, the thing or person doing the action is the subject of the sentence, and the thing or person receiving the action is the object. So:
Sam read the book.
Sam is the subject doing the action,’ read’ is the verb and the book is the object receiving the action.
What’s the problem?
The problem with passive is that the thing or person receiving the action becomes the subject of the sentence, but he, she or it isn’t actually doing anything. They are having something done to them. The first sentence isn’t grammatically wrong – it makes complete sense, but it sounds unnatural and forced. Another issue with passive voice is that it can be wordy. For example:
Passive
It was thought by most people that I killed my husband because he cheated on me.
Contrast the active:
Most people thought I killed my husband because he cheated on me.
Alison Williams Writing 