Question

When is it an appropriate choice in writing to use the passive voice

Answer 1

You can use it when the actor is unknown or when the actor is  irrelevant. hope this helped :)

Answer 2

Answer:

When the subject (person or thing) performing the action is not relevant.

Explanation:

The Passive Voice when writing or speaking is used when you wish to focus the attention on the person or thing affected by the action; instead of focusing on the person or thing who/that performs the action. I hereby give you an example.  

• Active sentence: They checked the letters on the mailbox.  (Who sent the letters?)
• Passive sentence: The letters were checked on the mailbox. (What was sent?)

As you can see, the second option does not include a subject/pronoun/person, and even if it were, the most remarkable there would be the letters and not the person who performed the action, whereas in the first example, it is remarkable the fact that “they” sent the letters; not you, not me. You can as well, include a name or be more specific:

• The men checked the letters on the mailbox

• The letters were checked on the mailbox by the men.