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Line of Force

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Lines of Force Definition

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In Physics, lines of force is the path followed by an electric charge. They are free to move in an electric field or a mass free to move in a gravitational field. Lines of force are lines in any source field, where the tangent drawn at any point gives the field direction at that point and the density of that gives the magnitude of the field. 

The concept of lines of force was introduced in the 1830s by the English scientist Michael Friday. Here we will discuss what is magnetic lines of force as well as electric lines of force and their properties.

In physics, lines of force is an imaginary line that represents a field of force, such as an electric or magnetic field.  If we draw a tangent at any point on the lines of force gives the direction of the field vector at that point.

Magnetic Lines of Force

Since no isolated unit pole has ever been discovered in the case of a magnetic field, the field lines are called lines of force only. An electric charge that travels along a magnetic field line undergoes no magnetic force.

Properties of Lines of Force 


Below We have Discussed the Properties of Magnetic Lines of Force:

  • Magnetic lines of forces always emerge from the north pole and it merges at the south pole.

  • As the distance between the poles increases, the density of magnetic lines also decreases.

  • The direction of field lines inside the magnet starts from the South Pole and end at the North Pole.

  • Two magnetic lines of force can never intersect each other at any point.

  • The strength of the magnetic lines of force is similar throughout the magnetic field and it is proportional to how close the lines of force are.

Force Line

Force lines is a technique that we use in solid mechanics for the visualization of internal forces in a deformed body. A force line graphically represents the internal force that is acting within a body across imaginary internal surfaces. These lines of forces show the internal forces and their directions.

Electric Lines of Force 

Electric Lines of Force Definition - Electric field lines are the way of visualizing electric fields. Electrical lines of force are described as a way or path. It can be straight or curved lines so that the tangent gives the direction of the intensity of the electric field at that point.

An electric line of force is an imaginary line that is a continuous line or curve that we draw in an electric field such that tangent to it at any point gives the direction of the electric lines of force at that point. The direction of a line of force is in the direction where a small free positive charge will move along the line. It always travels from positive charge to negative charge.

The electric lines of force represent the field of a positive electric charge in space.  It consists of a family of straight lines that radiate uniformly in all directions from where the charge originates. A second positive charge placed in the field that will travel radially away from the first charge.

Properties of Electric Field Lines

  • The field lines never intersect each other.

  • Electric lines of force contract longitudinally.

  • They expand laterally.

  • The magnitude of charge and the number of field lines, both are proportional to each other.

  • The starting point of the field lines is at the positive charge and the ending point is at the negative charge.

  • A single charge must be used for the field lines that either start or end at infinity.

Properties of Electric Lines of Force

  • Each electric line of force is conceptually imagined it does not have any physical existence.

  • The total number of lines of force that emerges from a charged body is equal to the charge of the body measured in Coulomb.

  • Each electric line of force originates from the positive charge and terminated to the negative charge.

  • A tangent drawn at any point on an electric line of force indicates the direction of the electric field lines at that point in the field.

  • Each electric line of force emerges normally from the surface of the charged body.

  • Electric lines of force contract only longitudinally.

  • Electric lines of force can expand laterally.

  • There are no two electric lines of force cross each other.

  • In the same direction, the electric lines of force repel each other.

  • The electric lines of force in opposite directions attract each other.

  • No lines of force can exist inside the conductor.

Difference between Magnetic and Electric Lines of Force

The differences between magnetic and electric lines of force are given below:

Magnetic Lines of Force

(1)  It is always in a close loop.

(2)  Magnetic lines of force can pass through iron more easily as compared to air.

(3)  Outside the body of the magnet, the direction of magnetic field lines is from the north pole to the south pole.

(4)  Magnetic fields formed from the motion of the charge, or the current.

Electric Lines of Force 

(1)  They never form a close loop.

(2)  Electron moves from positive to negative 

(3)  They have a static charge.

(4)  Electric fields are the result of the strength of the charge.

FAQ (Frequently Asked Questions)

Q1. Are Magnetic Lines of Force Continuous?

Ans: Magnetic lines of force represent continuous curves that originate from the north pole of a magnet and end at the south pole. Inside the magnet, these lines travel from the south pole to the north pole. Therefore, the magnetic lines of force are continuous.

Q2. Define Magnetic Lines of Force?

Ans: Magnetic lines of force are defined as curved lines which are used for the representation of the magnetic field. These lines of forces do not exist in reality but they are imaginary lines that pass through the pattern of the magnetic field. The origin of magnetic lines of force is the North Pole and it ends at the South Pole.

Q3. Can Two Electric Lines of Force Intersect Each Other? Give the Reason Why.

Ans: The two electric lines of force never intersect each other because, at the point of intersection when we draw a tangent, two tangents can be drawn to the two lines of force. This means that there are two directions of electric field at the point of intersection, that can not be possible.