"Where have you bought that lovely sweater"?

Hello Anonymous

You are trying to use the present perfect tense which suggests some connection with the present therefore incorrect. You should say, "Where did you buy that lovely sweater?" - Simple Past (you did it yesterday, it happened in the past).

The present perfect : I have (just) bought this sweater and now I don't like it.

Chief CookHello Anonymous

You are trying to use the present perfect tense which suggests some connection with the present therefore incorrect.

??

The connection is the sweater that my friend is wearing in the present moment.

I do agree with Chief Cook... A question starting with "where" amounts to asking "when", so the grammatical way is to use the simple past.

Hello, Anon!

Don't rack your brains and just memorize that a question starting with "when" need Past Simple Tense but never Present Perfect. And if "where" amounts to asking "when", as Pieanne said, then you should use Past Simple in that sentence.

:-)

The wearing of the sweater may be continuing into the present but the buying of it was firmly in the past, therefore 'Where did you buy that lovely sweater?'.

Is it correct to ask:

"Why have you come here?"

I mean if it is serviceable to use Present Perfect.

Yes; the point is that the person is "here". It's about the same as asking "why are you here?"

Pieanne, thanks! I wanted to make certain.

Anon, there is a good way to determine if Present Perfect may be used. It is always possible to replace Present Perfect sentences by Present Inderfinite sentences. For example:

1. I have broken my pencil. (My pencil IS BROKEN.)
2. Has the secretary come? (IS the secretary here?)
3. I have opened the window. (The window IS OPEN.