Electrostatic Field

      As we have seen in the previous article that unlike charges attract and like charges repel each other. Positively charged particle exerts a force of attraction on negatively charged while exerts a force of repulsion on positively charged particle. It must be kept in mind that the second charged particle also produces the electrostatic force on the first particle. So, it can be concluded that the space around the charge is always under the stress and exerts a force on another charge which is placed around it. The region or space around a charge or charged body in which the influence of electrostatic force or stress exist is called electric field or dielectric field or electrostatic field.
1.1 Electric Lines of Force
      The electric field around a charge is imagined in terms of presence of line of force around it. The imaginary lines, distributed around a charge, representing the stress of the charge around it are called as electric or electrostatic lines of force. The pattern of lines of force around isolated positive charge is shown in Fig 1(a). while the pattern of lines of force around isolated negative charge is shown in Fig 1(b). such lines of force originate from the positive charge and terminate on the positive charge, when this charges are placed near each other. They exert the force of attraction on each other. This is shown in Fig 1(c). while when two like charges are near each other, such lines will be in opposite direction as shown in Fig 1(d). there exists a force of repulsion between them.

Note: 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.
1.2 Properties of Electric Lines of Force
      The properties of electric lines of force are,
1) The lines of force always originate from a positive charge and terminate at negative charge.
2) They always enter or leave a conducting surface, normally.
3) They are always parallel and never cross each other.
4) The lines traveling in the same direction repel each other, while traveling in the opposite directions attract one another.
5) They behave like a stretched rubber band and always try to contract.
6) They pass only through the insulating medium between the charges and do not enter the charged bodies.
Note: Hence, they cannot from a closed loop as in case of the magnetic lines of force


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