Electric Lines of Force or Electric Field Lines

The electric lines of force are purely a geometrical construction, which help us to visualise the nature of electric field in the region. They have the following characteristics:

1. The tangent to electric lines of force at any point gives the direction of electric field at the point.
    
2. In free space, they are continuous curves which emerge from positive charge and terminate at negative charge.
    
3. They do not intersect each other, If they do so, then it would mean two directions of electric field at the point of intersection, which is not possible.
    
4. The density of field lines represent strength of electric field in the region.

Field Lines in Some Cases

(a) Positive point charge

Field lines have spherical symmetry

(b) Negative point charge

Field lines have spherical symmetry

(c) Two similar charges of equal magnitude

(d) Two similar charges of unequal magnitudes

(e) Two dissimilar charges of equal magnitudes