The field lines never intersect each other. The field lines are perpendicular to the surface of the charge. The magnitude of charge and the number of field lines, both are proportional to each other. The start point of the field lines is at the positive charge and end at the negative charge.

Suppose that there are two positive charges - charge A (Q A) and charge B (Q B) - in a given region of space. Each charge creates its own electric field. At any given location surrounding the charges, the strength of the electric field can be calculated using the expression kQ/d 2.

The number of field lines originating or terminating at a charge is proportional to the magnitude of that charge. A charge of 2 q will have twice as many lines as a charge of q. At every point in space, the field vector at that point is tangent to the field line at that same point.

Field lines must begin on positive charges and terminate on negative charges, or at infinity in the hypothetical case of isolated charges. The number of field lines leaving a positive charge or entering a negative charge is proportional to the magnitude of the charge.