Tag: What is Electric Field Line

Electric Field Lines | Properties | Examples

Electric Field-

 

Before you go through this article, make sure that you have gone through the previous article on Electric Field.

 

We have discussed-

  • Electric field is the space around an electric charge in which its effect can be experienced.
  • Every charge creates an electric field in the space around itself.
  • This electric field extends till infinity.

 

There are following 4 types of electric field-

 

 

In this article, we will discuss about Electric Lines of Force.

 

Electric Field Lines-

 

An electric field line or Electric Line of Force may be defined as-

 

It is defined as imaginary line in an electric field,

the tangent to which at any point on it represents the direction of electric field at that point.

OR

It is defined as the imaginary path traversed by a unit positive charge in an electric field.

OR

It is defined as the curve along which a unit positive charge tends to move if free to do so in an electric field.

 

It is important to note that-

  • The electric lines of force are imaginary curves.
  • But the electric field represented by them is real.
  • The term “lines of force” is misnomer.
  • It is more appropriate to call these lines as “electric field lines”.

 

Properties of Electric Field Lines-

 

Following are some of the important properties of electric lines of force-

 

Property-01:

 

  • The lines of force are continuous smooth curves.
  • They do not have any breaks.

 

Property-02:

 

  • The lines of force originate out of a positive charge and terminates on a negative charge.
  • If there exists a single charge, then lines of force end at infinity.
  • The lines of force cannot form closed loops.

 

Property-03:

 

  • The tangent to a line of force at any point gives the direction of electric field at that point.

 

Property-04:

 

  • No two lines of force can cross each other.

 

Property-05:

 

  • The lines of force have a tendency to contract longitudinally.
  • The lines of force have a tendency to exert a lateral pressure on neighboring lines of force.

 

Property-06:

 

  • The lines of force are always normal to the surface of a conductor on which the charges are in equilibrium.

 

Property-07:

 

  • The relative closeness of the lines of force gives a measure of the strength of the electric field.
  • Closer the lines of force, stronger is the electric field.

 

Property-08:

 

  • The lines of force do not pass through a conductor.

 

Electric Lines Of Force For Different Charged Conductors-

 

Let us represent the electric lines of force for the following-

  • Electric lines of force of a positive point charge
  • Electric lines of force of a negative point charge
  • Electric lines of force of an electric dipole
  • Electric lines of force for a system of two equal positive point charges

 

Case-01: For Positive Point Charge-

 

If there exists only one positive point charge, then-

  • The electric lines of force originate from that charge.
  • The electric lines of force terminate at infinity.

 

 

Case-02: For Negative Point Charge-

 

If there exists only one negative point charge, then-

  • The electric lines of force originate from infinity.
  • The electric lines of force terminate at that charge.

 

 

Case-03: For Electric Dipole-

 

Electric dipole is a system of two equal and opposite charges separated by a small distance.

If there exists an electric dipole, then-

  • The electric lines of force originate from the positive charge.
  • The electric lines of force terminate at the negative charge.

 

 

Case-04: For A System Of Two Equal Positive Point Charges-

 

If there exists a system of two positive charges, then-

  • They exert a lateral pressure  on account of repulsion between like charges.
  • The electric field is zero at the middle point on the line joining the two charges.
  • This point is called neutral point from which no line of force passes.

 

 

Conceptual Questions Based On Electric Lines Of Force-

 

Question-01:

 

Why electric lines of force are smooth continuous curves?

 

Answer-

 

Electric lines of force are smooth continuous curves without any breaks because-

  • Their discontinuity would indicate that the charge suddenly vanishes and reappears.
  • This is absurd.

 

Question-02:

 

Why no two electric lines of force can intersect each other?

 

Answer-

 

No two electric lines of force can intersect each other because-

  • If they intersect, then there will be two tangents at the point of intersection.
  • Hence, two directions of the electric field at the same point will exist which is impossible.

 

 

Question-03:

 

Why electric lines of force contract longitudinally and exerts a lateral pressure?

 

Answer-

 

  • Electric lines of force contract length-wise on account of attraction between unlike charges.
  • Electric lines of force exert a lateral pressure on account of repulsion between like charges.

 

Question-04:

 

Why electric lines of force are always normal to the surface of a conductor on which the charges are in equilibrium?

 

Answer-

 

This is so because if the lines of force are not normal to the surface of a conductor, then-

  • There exists a component of the field \overrightarrow{E} parallel to the surface.
  • This would cause the electrons to move and set up a current on the surface.
  • But no current flows in the equilibrium condition.

 

Question-05:

 

Why electric lines of force never pass through a conductor?

 

Answer-

 

Electric lines of force never pass through a conductor because electric field inside a charged conductor is zero.

 

To gain better understanding about Electric Lines of Force,

Watch this Video Lecture

 

Next Article- Electric Flux

 

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