What are magnetic field lines? How is the direction of a magnetic field at a point determined ? Mention two important properties of magnetic field lines.

Explanation

Magnetic field lines are used to represent a magnetic field. A field line is the path along which the north pole of a small compass tends to move. The direction of the magnetic field at a point is given by the direction in which north pole of compass placed at that point would take.
Two properties of magnetic field lines are as follows:
(i) In air field lines start from N-pole and end at S-pole.
(ii) No two magnetic field lines can ever intersect at any one point.