Electric lines of force
The concept of field lines was introduced by Michel Faraday as an aid in visualizing electric and magnetic fields.
Electric line of force is an imaginary straight or curved path along which a unit positive charge tends to move in an electric field.
The electric field due to simple arrangements of point charges
Properties of lines of forces for charges:
1. Lines of force start from positive charge and terminate at negative charge.
2. Lines of force never intersect.
3. The tangent to a line of force at any point gives the direction of the electric field (E) at that point.
4. The number of lines per unit area, through a plane at right angles to the lines, is proportional to the magnitude of E. This means that, where the lines of force are close together, E is large and where they are far apart, E is small.
5. Each unit positive charge give rise to 1/Є0 lines of force in free space. Hence number of lines of force originating from a point charge q is N=q/ Є0 in free space.