electromagnetism - What is the direction of magnetic lines of force inside a bar magnet?

So basically , we all know the direction outside the magnet its from NORTH to SOUTH. but what i don't understand is that what is the direction inside is it the same ??

Answer

Suppose you look at the magnetic field lines generated by an electric current flowing in a loop. They look something like this:

(image from HyperPhysics)

So the field lines travel outwards from one side of the loop, the North pole, round to the other side, the South pole, then go inside the loop to complete their circuit. This has to happen because magnetic field lines cannot begin or end so they always have to form closed loops.

In a bar magnet the magnetic field comes from electrons in the material making up the magnet. Electrons generate a magnetic field just as a current loop does, and while the magnetic field from a single electron is tiny the gazillions of electrons in a bar magnet combine their fields to form the overall magnetic field of the bar magnet.

So if you followed an individual field line from the North pole of a bar magnet you'd find it wound round to the South pole then went inside the magnet so it's now travelling South to North inside the magnet. Eventually the field line would lead to electron that created it, then through the electron and back to the North pole where it leaves the bar magnet again.