The concept of field line was introduced by Michael Faraday as an aid in visualizing electric and magnetic fields.

Electric line of force is an imaginary straight or curved path along which a unit positive charge tends to move in an electric field.

The electric field due to simple arrangement of point charges are shown in diagram.

Properties of electric lines of force :

The electric lines of force have the following properties-
  1. The lines of force start from the positive charge and end at the negative charge.
  2. The lines of lines of originate( from a positive charge ) or the terminate (at a negative charge) always at right angles to the surface of the charge.
  3. The lines of force do note pass through a conductor. i.e. It indicate that the electric field inside a conductor is always zero.
  4. The lines of force never intersect each other.
  5. the relative closeness of lines of force in different regions of space gives the idea about the relative strength of the electric field in the different regions.
  6. The lines of force contract longitudinally i.e. lengthwise. 
  7. The lines of force exert a lateral pressure on each other.