Suppose that you are a teacher and you are asking to yor students in the classroom.

[lhn]

Originally Posted by kjelladrian

Hi Ihn and everybody!
I'm Kjell from Sweden, and, hopefully, I'll be a certified teacher in English after the next term. This is a very late answer, but when I saw this interesting question I thought it was worth a reply.
When you use spoken English in this context, and you're not looking at any particular pupil, because you're aiming the question at the whole class, both sentences are equally correct. Because the subject "you" covers both second person singular and second person plural. So here, you as a speaker decide with your body language whether you direct the question at a particular student or at the whole class.
In a written text, though, you of course have to make it clear to the reader to whom you are aiming the question.
Best/Kjell

Hi Kjell,
But I know this. When you are asking to all students in your classroom, I would like to know which one to use, that is, Simple past or Present Perfect Form:
Did you do your homework?

Have you done your homework?

Now, what is your answer?

Thank you for your kind comment.

[lhn]

Originally Posted by Casiopea

I use both. I use "Have you ... ?" when time isn't a factor, and "Did you ... ?" when time is a factor. For example,
Past Simple (time is important; the "when")
I gave you this assignment last week. Did you do it?
Present Perfect (the act is important)
Take our your homework. Have you done it?
All the best.

Where have you been??? I have been waiting for you for a long time. You are a very kind man Casiopea. Thanks...

[kjelladrian]

Originally Posted by lhn

Suppose that you are a teacher and you are asking to your students in the classroom:
Did you do your homework?
or
Have you done your homework?
Which one is correctand why?

Hi again boys and girls!
We could start a society in this subject and meet once a year to eat and drink wine and discuss this subject further
I apparently misunderstood your question, Ihn, and answered what you probably already knew. That wasn't my intention, sorry. I'm of course also humble to a native speaker of English as the moderator Casiopeia evidently is. He apparently knows of the more subtle nuances of the language that I, until now, hadn't thought about. Thank you for that Cassiopeia! I have learnt something new!