Why we cant separate noth and south poles

No - we cannot. The magnetic effect is due to current loops which produce what is called a dipole field. Magnets exist only in the form of dipoles with two ends, a north and a south. When a bar magnet is split into two pieces, you don?t get a separate north part and a south part. Rather you get two new, smaller magnets, each with a north and south end.

For your information, a magnetic 'monopole' has been predicted in quantum physics, but scientists have not seen one so far.