Active voice sentence to passive voice sentence

Let me teach you how to change sentences from active voice to passive voice:

REMINDER : Passive voice sentences always have the word by follow by a subject from active voice sentence. The verb must change to past participle.

SIMPLE PRESENT TENSE
            is / are + past participle

Ex : Tom eats the pear ------> The pear is eaten by Tom.
Subject : Tom
Object : the pear
Verb: eats to eaten

SIMPLE PAST TENSE
         was/ were + past participle 

Ex : Tom ate the pear --------> The pear was eaten by Tom. 
Subject : Tom
Object : the pear
Verb : ate to eaten