An electric field line is, in general is the path followed by a +ve charge when kept in an electric field.
An arrow on the curve is obviously necessary to specify the direction of electric field from the two possible directions indicated by a tangent to the curve. A field line is a space curve, i.e., a curve in three dimensions.
Properties of Electric field lines: –
1. The electric lines of force are imaginary lines.
2. A unit positive charge placed in the electric field tends to follow a path along the field line if it is free to do so.
3. The electric lines of force came out from a positive charge and came in a negative charge.
4. The tangent to an electric field line at any point gives the direction of the electric field at that point.
5. Two electric lines of force can never cross each other.Because If they do, then at the point of intersection, there will be two tangents. It means there are two values of the electric field at that point, which is not possible.
Further, electric field being a vector quantity, there can be only one resultant field at the given point, represented by one tangent at the given point for the given line of force.
6. Electric lines of force are closer (crowded) where the electric field is stronger and the lines spread out where the electric field is weaker.
7. Electric lines of force are perpendicular to the surface of a positively or negatively charged body.
8. Electric lines of force contract lengthwise to represent attraction between two unlike charges.
9. Electric lines of force exert lateral (sideways) pressure to represent repulsion between two like charges.
10.The number of lines per unit cross – sectional area perpendicular to the field lines (i.e. density of lines of force) is directly proportional to the magnitude of the intensity of electric field in that region.
11. Electric lines of force do not pass through a conductor. Hence, the interior of the conductor is free from the influence of the electric field.
i.e. E in a conductor is 0
12. Electric lines of force can pass through an insulator.
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