Why magnetic field are from south to north pole inside bar magnet?

Question

magnetic field lines are from north pole to south pole outside a bar magnet but its direction is from south pole to north pole inside it. Why and what causes it?

Answer 1

you can understand this more easily if you have a look at the magnetic field lines surrounding an electromagnet coil. each line loops around the coil in an unbroken path and the direction of the field is consistent along the entire length of every loop. these characteristics of magnetic field lines are captured in Maxwell's equations.

if the field lines were not loops- if, instead, all the field lines pointed from the north pole to the south pole inside the magnet as well as outside- this would mean that the magnetic poles in this case were monopoles, which as far as has been determined to date, do not exist in the real world except as mathematical constructs in certain unified field theories.