Electric Field Lines

When a point light positive charge is placed in a certain area, the path it follows due to electric force is called an electric field line. Electric field lines spread from positive charges.

If there is a high density of electric field lines at a point, ( if a higher number of field lines pass through that point) the electric field intensity of that point is high. If no lines of electric field lines pass through a point, the electric field intensity at that point is zero. (figure 02)

Properties of electric field lines

1. Electric field lines never intersect each other
2. Electric field-lines may start from positive charges and end at negative charges
3. Electric field-lines may start from positive charges and end at infinity
4. Electric field lines may start from infinity and end at negative charges
5. If there are no field lines at a point, the electric field intensity of that point is zero. That point is known as the 'Neutral point' (Figure 02).
6. There is always repulsion between field lines
7. Electric field-lines are perpendicular to the charged surface

Electric flux

Electric flux is the number of electric field lines across a unit area. The electric flux that passes perpendicular to a unit area, is the electric field intensity of that area.

Where,

• φ  = Electric flux
• E = Electric field intensity
• A = Surface area

If the field lines are not perpendicular to the surface, the electric flux can be calculated as follows.

Where θ is the angle between the surface and the field lines.