Rules for Electric Field Lines

Rules for electric field lines:

The lines are directed : they originate on and point away from positive charges, and terminate on and point towards negative charges. They can also originate from or terminate at infinity.
At any given point in space, the tangent to the line is the direction of the Electric field vector at that point.
From a charge Q placed in a medium of permittivity e, the number of lines originating or terminating is Q / e.

Consequences of these rules:

Two lines of force can never intersect.
Lines of force intersect conducting surfaces normally, i.e. at a 90° angle.

In the drawings above, you can see the electric field lines of three different charge configurations. One conventionally uses the same number of field lines per charge unit in all drawings. However, the value of that proportionality factor is arbitrary, only the relative number of field lines of one area as compared to another will allow us to make a statement regarding the strength of the E-field.