electromagnetismmagnetic fields
I am confused about the point from where magnetic field lines originate. Do they always start from the same point or are there infinitely many points from where a magnetic line originate?
If the second one is correct, then can more than one point originate from any one of those points?
I want to ask the same thing for the point where they come back to the south pole of the magnet.
You are correct in saying that the pole near the Arctic circle is really the south pole of the Earth's magnetic field because the north pole of a bar-magnet points towards it. (Wiki)
That said, it is purely convention what you define on a bar magnet to be north and south - we've named the side that points towards the Arctic circle to be the north pole of the bar magnet, and since people don't immediately identify this seeking behavior as opposite poles attracting, we tend to think the earth's field at the Arctic circle is also a north pole when it is strictly speaking, a south magnetic pole.
Also, I would add that the magnetic poles don't coincide with the geographic poles - the latter define the points of intersection of the Earth's rotational axis with the surface of the Earth. We know for a fact that the magnetic poles have shifted (even reversed) with respect to the geographic poles during the history of the Earth. (Wiki)
Here are from wikipedia drawings of the field lines of two magnets in two orientations, like-like, like-unlike .
North pole to north pole
North pole to south pole.
The lines distort but do not intersect.
These field lines are solutions of the formal Maxwell differential equations. Differential equations do not give discontinuous solutions, as would be the case if two lines crossed. Discontinuities in the solutions when smooth boundary conditions exist are not possible, as in the drawings. Discontinuities can exist as singularities, which can only exist at the source of the field. The field lines themselves follow smooth functions away from sources.
Mawell's equations have been continually validated by an enormous number of experiments and applications and thus we trust the descriptions of nature that the solutions give.
Best Answer
There is no particular "point of origin" in case of magnetic field lines. This is because magnetic field lines form continuous closed loops. Even inside permanent magnets (like a bar magnet), magnetic field lines join from south to north poles. Also, magnetic field lines can't intersect, which means there would be no common point from which two or more magnetic field lines could originate.