Chapter-1|Electric Charges and Fields | NCERT 12th Physics:
Electric Field Lines:
An electric field line in general is a curve drawn in such a way that the tangent to it at each point is in the direction of the electric field at that point.
Properties of Electric Field Lines:
1. Electric field lines start from positive charge and end at negative charges. In case of single charge they may start or end at infinity.
2. Tangent to any point on electric field lines shows the direction of electric field at that point.
3. Two field lines can never intersect each other because if they do so, then two tangent drawn at that point will represent two directions of electric field at that point, which is not possible.
4. In charge free region, electric field lines can be taken to be continuous curve without any breaks.
5. Electric field lines do not form closed loop.
6. Electric field lines are perpendicular to the surface of charged conductor.
7. Electric field lines contract lengthwise to represent attraction between two unlike charges.
8. Electric field lines exert sideways pressure to represent repulsion between two like charges.