Give the characteristics of magnetic field lines.

The properties of magnetic field lines are as follows :

$(i)$ The magnetic field lines of a magnet form continuous closed loop. This is unlike the electric dipole where these field lines begin from a positive charge and end on the negative charge or escape to infinity.

$(ii)$ The tangent to the field line at a given point represents the direction of the net magnetic field $\overrightarrow{\mathrm{B}}$ at that point.

$(iii)$ The larger the number of field lines crossing per unit area, the stronger is the magnitude of the magnetic field $\overrightarrow{\mathrm{B}}$. In figure $(a)$ $\overrightarrow{\mathrm{B}}$ is larger around region $(b)$ than in region $(a)$.

$(iv)$ The magnetic lines do not intersect for if they did, the direction of the magnetic field would not be unique at the point of intersection one can plot the magnetic field lines in a variety of ways.

If they do it means at the point of intersect the tangent is showing two different directions which is not possible.