Question

Why does a magnetic compass needle deflect when a bar magnet or a current carrying loop is brought near it.

Answer 1

A compass needle is a small bar magnet. When it is brought near a bar magnet, its magnetic field lines interact with that of bar magnet. Hence it gets deflected when brought near a bar magnet.
Hope it will help!

Answer 2

When a magnetic bar and current carrying loop brought near the magnetic compass it shows defloration due to the magnetic field present between them