(a) Equidistant parallel line indicates a uniform magnetic field in a given region.
(b) Properties of magnetic field lines are: The magnetic field lines of a magnet form continuous closed loops, i.e. outside the magnet, they emerge from north pole and merge at the south pole and inside the magnet, the direction of field lines is from its south pole to its north pole. The degree of closeness of field lines indicates the strength of magnetic field. Field lines never cross each other.
