7.1 Properties of electric field lines

  Electrostatics

1. The tangent to a line at any point gives the direction of $\overrightarrow E $ at that point. This is also the path to which a positive test charge will tend to move if free to do so.
   
   
2. Electric field lines always begin with a positive charge and end on a negative charge and do not start or stop in mid space.
   
   
3. The number of lines leaving a positive charge or entering a negative charge is proportional to the magnitude of the charge.
   
   
4. Two lines can never intersect. If it happens then two tangents can be drawn at the point of intersection. It means two directions of the electric field at that point which is not possible.
   
   
5. In a uniform field, the field lines are straight, parallel and uniformly spaced.
   
   
   
   
   
   
6. The electric field lines can never form closed loops as a line can never start and end on the same charge.
   
   
7. Electric field lines also give us an indication of the equipotential surface ( a surface which has the same potential).
   
   
8. Electric field lines always flow from higher potential to lower potential.
   
   
9. In a region where there is no electric field, lines are absent. This is why inside a conductor (where an electric field is zero) there cannot be any electric field line.
   
   
10. Electric field lines start or end normally from the surface of a conductor.