Question

why a bar magnet/solenoid always rest in north-south direction?

Answer 1

A current carrying solenoid behaves like a bar magnet as shown below:

Now, we know our earth is assumed to have a large magnet at its center with its north pole towards the geographic south pole and the south pole towards the geographic north pole. This is why the solenoid when freely suspended will align in such a way that its South points towards earth earths geographic South pole.


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