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Coulombic Force

Last updated date: 27th Feb 2024
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What is the Electrostatic Force?

The word Electo in electrostatic is for electric charges and static means at rest. So, the study of force between two like or alike charges is called electrostatic force.

Any stable atom always contains the electrostatic force of attraction. An electrostatic force is also known as the Coulombic force. It is the force of attraction between two opposing charges, i.e., protons and electrons. Here, the strong electrostatic force of attraction between them stabilizes the atomic particle.

On this page, we will define electrostatic force and discuss the real-life applications of electrostatic force in detail.

Define Electrostatic Force

An electrostatic force or the Coulombic force is defined as the force of attraction or repulsion between two like and unlike charges, respectively. The two charges bear equal magnitude but opposite charges and are separated by some distance.

An imaginary line exists between these two charges to mark their distance from each other. Also, the charges have the square of the distance between them.

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Now, we will learn to find the electrostatic force between the two charges, viz: q1 & q2 in the following context:

Electrostatic Force

Take a balloon and a piece of wool. Now, rub the balloon with this piece of wool, a heat generated on the balloon’s surface.

Bring a few pieces of paper near to this balloon, you see that pieces of paper get attracted to the balloon. It is because an electrostatic force of attraction builds between the balloon and the pieces of paper.

Coulomb’s Law

We can quantify the electrostatic force between two charged particles by using Coulomb’s law. Coulomb’s law usually applies to point charges and gives a relationship between the electrostatic force, the magnitude of the charges, and the distance between them. According to this law, the force between the two particles is stated in the following manner:

  • Electrostatic force varies proportionally with the product of the magnitude of the charges

  • Varies inversely with the square of the distance between the two equal and opposite charges.

Coulombic Force

A Coulombic force can be explained by the following equation:

\[F \alpha \frac{q_{1}q_{2}}{r^{2}}\]


q1 = a positive/negative charge or vice versa

q2 = a negative/positive charge or vice versa

r² = the distance between the two charges (both of equal and opposite magnitude)

Now, removing the sign of the proportionality constant, we rewrite the equation as;

\[F=K \frac{q_{1}q_{2}}{r^{2}}\]

Here, k is the constant and it is known as the electrostatic constant or the force constant. 

Define Coulomb Constant

The Coulomb constant was named after the French physicist named Charles-Augustin de Coulomb who introduced Coulomb's law.

The value of ‘k’ is approximately equal to 8.987 5517923 (14) x 109 kg.m3.s-2.C-2

According to the above equation (2), F disappears when r approaches infinity. Thus, at infinity or a large distance, the electrostatic force reaches zero. Scientifically, the range of F is infinite.

The work done W by the force F on a particle is the product of the force and the displacement d. The equation is as follows:

W= F x d

The work done in moving the charged particle from one position to another is independent of the path taken. Hence, the electrostatic force is conservative in nature.

Examples of Electrostatic Force

  • The rubbing of clouds produces electrostatic charges. These charges get neutralized by passing through the atmosphere until they reach the neutral ground. We perceive this phenomenon as lightning.

  • After combing your hair, if you bring the wet comb close to a piece of paper, an electrostatic force of attraction between the comb and trace of the paper develops, and the paper sticks with the comb.

  • A silk shirt sticks to the body because of charged particles on the shirt. The same phenomenon applies to a woollen pullover when taking off.

  • Getting out of a vehicle on a warm, dry day and touching its door gives us charges.

  • Grains of sugar get attracted to the inside surface of a container due to electrostatic forces.

  • The surface of the truck carries a lot many charges and when any vehicle passes the truck, the electrostatic force generates between the charged particles on the truck’s surface and the charges present in the air. 

Point to Note:

Electrostatic forces are present at places where charged particles interact through a polar medium. Hence, electrostatic forces are particularly crucial for ceramic materials in polar media viz: water and ethanol. The electrostatic forces are usually stronger and have a longer range than all other surface forces.

Applications of Electrostatic Force

The electrostatic force carries multiple real-life applications, and a few of these are discussed below:

  • Photocopying machines

  • Laser and ink-jet printers

  • Van der Graaff generator

  • Smoke precipitator, and

  • CCD (charged-couple device) camera

FAQs on Coulombic Force

1. Why Do Trucks Have a Hanging Chain at Their Back?

Ans - A truck carries a high magnitude of charges around its surface. When a vehicle pasts the truck, the air particles moving past it too carry charges with itself. So, these two charges being equal and opposite in magnitude develop a large cloud of charge. A time comes when this large cloud bursts and a truck especially, a petrol tank encounters firing. 

So, a chain behind the truck acts as a facilitator to transfer the charge to the ground. Here, this facilitator saves the truck from encountering an accident.

This is one of the best-known phenomena of electrostatic force.

2. State the Comparison Between the Electrostatic and Gravitational Forces.

Ans - Similarity

a) Both are central forces. i.e, both act along the line joining the centres of two interacting bodies.

b) Both the forces obey the law of inverse square of the distance.

c) Both forces are conservative in nature, i.e, the work done by them is independent of the path followed.

d) Both forces can work in a vacuum.


1. Gravitational forces are attractive in nature, while the electrostatic forces can either be attractive or repulsive.

2. Gravitational forces do not depend on the medium, while the electrostatic force definitely depends upon the medium.

3. Electrostatic forces are larger than gravitational forces.