(a) A current carrying solenoid behaves like a magnet when its end one acts like a north pole and the other end as a south pole. So, if a current-carrying solenoid is suspended freely by tying a thread in the middle, it will come to rest pointing in the north and south directions in the say manner like a freely suspended bar magnet.

(b) We can determine the north and south poles of a current-carrying solenoid by using a bar magnet. This can be done as follows: We bring the north pole of a bar magnet near both the ends of a freely suspended current-carrying solenoid. The end of solenoid which will be repelled by the north pole of bar magnet will be the north pole of the solenoid. And the end of solenoid which will be attracted by the north pole of the bar magnet and move towards it, will be its south pole.