A magnetic field line is a path along which a free north pole tends to move.
Characteristics :
(i) Outside a magnet, the magnetic field lines are directed from N-pole of the magnet towards S-pole. However, inside a magnet field lines are directed from S-pole to N-pole.
(ii) The relative strength of magnetic field lines is given by degree of closeness of the field lines. More crowded field lines mean a stronger field.
(iii) No two magnetic field lines can ever intersect each other.
Diagram: Magnetic field pattern of a current carrying circular loop.
