Electric Lines of Force

Electric Lines of Force

Electric lines of force in an electric field is defined as the paths along which a unit positive charge tends to move if it is free to do so.

The tangent drawn at any point on electric line of force gives the direction of electric field intensity at that point.

Note:It is also known as Electric Field Lines or Field lines of Electric force or Electric flux lines or simply electric fields.

Uniform field: A field is uniform in the given space if its field strength is same at every point in the given space.It is represented by straight, equispaced parallel field lines.

Example: The field produced by the parallel plates of a capacitor having uniform charge density is uniform.

Non-uniform field : A field is non-uniform in the given space if its field strength is different points in the given space.The figure shown below is the example of non-uniform field.

Example: Field of an isolated charge is not uniform. The field lines are radial and not parallel to one another.

1. Electric field at a point due to a negative source charge is directed towards this charge as shown in figure below.
2. Electric field at a point due to a positive source charge is directed away this charge as shown in figure below.

Properties of Electric Field lines

1. The electric field lines are directed away from a positive charge and directed towards a negative charge.
2. Electric field line are imaginary lines.
3. The tangent to an electric field line at any point gives the direction of the electric field at that point.
4. Two electric field line never cross each other. If two electric lines of force cross each other, then at the point of intersection, there will be two tangents. It means that there are two values of the electric field at that point, which is not possible.
5. The electric field line are crowded where the electric field is stronger and the lines spread out where the electric field is weaker.
6. Electric field line are perpendicular to the surface of a positively or negatively charged sphere.
7. Electric field line contract lengthwise to represent attraction between two unlike charges.
8. Electric field line exert lateral pressure on each other and hence repel each other to represent repulsion between like charges.
9. The number of lines per unit cross-sectional area perpendicular to the field lines (i.e., density of lines of force) is proportional to the magnitude of the intensity of electric field in that region.
10. Electric field line do not pass through a conductor.

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