Magnetic Field Lines

Interactions between magnets or a magnet and a piece of iron essentially represent action at a distance. This can be understood in terms of magnetic field. A very convenient method to visualize the direction and magnitude of a field is to draw the field lines.

• The direction of magnetic field vector B at any point is given by the tangent to the field line at that point.
• The number of field lines that pass through unit area of a surface held perpendicular to the lines is proportional to the strength of magnetic field in that region. Thus, the magnetic field B is large where the field lines are closer together and smaller where they are far apart.
• Outside the magnet, the field lines run from north pole to south pole and inside it, these run from south pole to north pole forming closed curves.
• Two magnetic field lines can never cross each other.