Option 1 states that the pole strength of the north-pole of a bar magnet is larger than that of the south-pole. This statement is incorrect because in a bar magnet, the north and south poles have equal strength. So, option 1 is not correct.

Option 2 states that when a piece of a bar magnet is bisected perpendicular to its axis, the north and south poles get separated. This statement is also incorrect because when a bar magnet is bisected, the resulting pieces still retain their north and south poles. So, option 2 is not correct.

Option 3 states that when a piece of a bar magnet is bisected perpendicular to its axis, two new bar magnets are formed. This statement is correct because when a bar magnet is cut, each piece acts as a separate magnet with its own north and south poles. So, option 3 is the correct statement.

Option 4 states that the poles of a bar magnet are unequal in magnitude and opposite in nature. This statement is incorrect because the poles of a bar magnet are equal in magnitude and opposite in nature. So, option 4 is not correct.

From analyzing all the options, we can conclude that option 3 is the correct statement about a bar magnet.