Electric Lines of Force and its Properties

What is Electric Lines of Force?

The electric field around a charge is imagined in terms of the presence of lines of force around it. The imaginary lines, distributed around a charge, representing the stress of the charge around it are called electric or electrostatic lines of force.

The pattern of lines of force around the isolated positive charge is shown in fig (a) while the pattern of lines of force around the isolated negative charge is shown in fig (b). Such lines of force originate from the positive charge and terminate on the negative charge when these charges are placed near each other. They exert the force of attraction on each other. This is shown in fig (c). While when two lines charges are near each other, such lines will be in the opposite direction as shown in fig (d). There exists a force of repulsion between them.

In general, the directions of the lines of force at any point is the direction of movement of a unit positive charge placed at that point, if free to do so.

Properties of Electric Lines of Force:

The properties of electric lines of force are-

• Electric/electrostatic lines of force are discontinuous curves. They start from a positively charged body and end at a negatively charged body.
• Tangent to the line of force at any point gives the direction of Electric Field Intensity at that point.
• No two electric lines of force can intersect each other.
• They always enter or leave a conducting surface, normally.
• The electrostatic lines of force exert lateral pressure due to repulsion between like charges.
• The electrostatic lines of force contract longitudinally due to attraction between unlike charges.
• Crowding of electrostatic lines of force represents a stronger electric field and vice versa.
• Electrostatic lines of force are imaginary and do not exist in reality.
• The number of electrostatic lines of force per unit area is directly proportional to the strength of the electric field.
• They pass only through the insulating medium between the charges and do not enter the charged bodies. Hence, they cannot form a closed loop as in the case of the magnetic lines of force.