The passive voice can be used if you don't know who preformed the action descried in the sentence.
TRUE
Create a sentence in passive voice
Telephone (Alexander Graham Bell)
The telephone was invented by Alexander Graham Bell
The cook cooked the rice.
The rice was cooked by the cook.
The dog was tricked by the cat. (This is an active sentence)
False
The worksheets are printed.
The printer printed the worksheets .
The farm owner takes care of the sheep.
The sheep is taken care of by the farm owner.
The painter painted a gigantic picture in France.
A gigantic picture was painted by the painter in France.
''The old man was murdered." (Passive to Active)
Someone/somebody murdered the old man.