Question

why a needle of compass only towards the north?

Answer 1

i think so due to magnetic effect

Answer 2

A compass points north because all magnets have two poles , a north pole and a south pole, and the north pole of one magnet is attracted to the south pole of another magnet. (You may have seen this demonstrated by a pair of simple bar magnets or refrigerator magnets pushed end to end.)

The Earth is a magnet that can interact with other magnets in this way, so the north end of a compass magnet is drawn to align with the Earth's magnetic field. Because the Earth's magnetic North Pole attracts the "north" ends of other magnets, it is technically the "South Pole" of our planet's magnetic field.