Source : http://www.englisch-hilfen.de/en/complex_tests/passive2/index.php
What I did : I did an online test on active and passive voice
What I learnt:
I learnt that for active voice, the subject does an action that is described as the verb. The sentence structure of an active voice sentence, for example : "I crushed a tin can", where the subject "I" acts upon the verb "crush"
However, in passive voice, the subject of the sentence is acted upon by some other agent. The sentence now becomes "The tin can was crushed by me". "tin can" becomes the subject, and the verb remains "crush".