I'm, we're, and he's are also built upon linking verbs and express a state of being.
Passive voice tends to conceal rather than reveal information.
In the sample sentence above, we do not know who mentioned the student's name or why he or she mentioned it. The telephone bill was paid last week. The policeman was concerned by the stories. After hearing them, he was convinced that at least one person had committed a serious crime. The senator made the decision.