Properties of Electric Field Lines:
(i) No field line originates or terminates in the space surrounding a charge. Every field line is a continuous and smooth curve originating from a positive charge and ending on a negative charge.
(ii) Field lines do not cross each other because if they do, as at the point P in Fig then two tangents can be drawn at the point of intersection, one to each field line. This means that electric intensity at such a point has two directions, which is not possible.
(iii) Wherever the field lines are:
Closer together, the field is strong.
Wherever the field lines are
(a) Far apart, the field is weak, which is the case when the field is non-uniform.
(b) parallel and equally spaced, the field is uniform.
(iv) Field lines do not pass through the conductor. This indicates that the electric field within the conductor is zero.
(v) The field lines are perpendicular to the surface of the conductor. Had it been not so, there would have been a component of the field along the surface of the conductor and a current would flow through it. But no current flows in such an electrostatic situation. Thus, the electric field just outside the surface of the conductor is perpendicular to its surface.
(vi) There exists a longitudinal tension in the field lines. It is this tension which explains attraction between two, unlike charges.
(vii) The field lines exert lateral pressure on each other. It is this lateral pressure which accounts for the repulsion between two like charges.