The Uses of Active and Passive Voice
Use the passive voice to:
Call attention to receiver of the action rather than the performer:
The professor was hit by three snowballs.
Point out the receiver of the action when performer is unknown or unimportant:
A love letter was slipped under the door.
The signs will be posted.
Avoid calling attention to the performer of the action (known as the "institutional
passive"):
The fines will be collected on Monday.