What is Coulomb’s law, Vector form, Formula, Applications — The Engineering Knowledge

5 min readNov 26, 2022

Hi, Guys I hope you all are fine and will be doing some fun in your daily life. Friends in today’s tutorial I am going to explain coulomb’s law. This law was first described by a French physicist in 1785, whose name was Charles-Augustin de coulomb’s law. This law is applicable to stationary charges. This law states that the force of attraction and repulsion between two charged particles is directly proportional to the product of the magnitude of charges AND inversely proportional to the square of the distance of charges between them. F12=F21=Kq1q2/r2.
Columb law is applicable to measure force between charged particles. This law is a very important law in physics, which helps us to solve different numerical problems and tells us about stationery charges. In this tutorial, I will explain its detailed description, solved equation, its application, limitations, etc. So, let’s get started with Introduction to Columbs law.

Introduction to coulomb’s law

Its mathematical expression is F x q1q2/r2, F= kq1q2/r2. In this equation F denotes force which is between two charges, q1 is the first charge q2 is the second charge, r is the distance between these two charges and K is proportional.
In this equation, K is constant its values depend on the medium between two charges.
If there is no specific medium in between two charges then there is free space is the medium, in this case, the values of k is
K=1/4piE0 In this equation E0 is an electrical constant, which is known as the permittivity of free space.
In si units its value is 8.8 after putting this value in the given eq we get the Coulomb’s law force in free space is F=q1q2/r
Columb force is a mutual force it means that if q1 exerts a force of q2 then q2 also exerts force on q1.

Explanation of Coulomb’s law

As we already know the force between two charges is mutual force, if we denote force exerted by on q2 by q1 is F21 and on q1 by q2 F12 then we have an equation like this
F12=-F21 in this equation minus sign shows that the direction of these forces is opposite.
If r21 is a unit vector that has a direction from q1 to q2 and r12 has a direction from q2 to q1 then we have an equation like this
Both forces are shown in given diagram.

Coulomb’s Law Definition

Coulomb law states that interaction between charged particles. That defines the number of electrostatic forces existing between eh two charged objects that is repulsion and repulsion
If the charges are the same they will have the force of repulsion and opposite charges will have the force of attraction

Coulomb’s Law Formula

In the above figure, you can see the formula of the coulomb law. This expression shows that the force existing between two charged particles is equal to the product of two charges Q1 and Q2 divided by the square of the distance between charges denoted with r. In this formula K is constant
The unit used for this force is Newton. Since distance is squared as the distance between two objects is doubled force between them decreases to four times

Coulomb’s Law vs Universal Law of Gravitation

There is some similarities exist between this two law but they are different
The electric force is stronger than gravity
In the below equations, you can see that there are different proportionality constants used for these two forces
In gravity, mass is used for force calculation, and for coulomb law charge is used to measure the force
Gravitational force is always attractive and electrostatic force is repulsive or attractive according to charges polarity for same charges will be repulsive and different charges will be attractive

Vector Form of Coulomb’s Law

As the force of electrostatic is like force so interaction between charges is a vector quantity that direction and magnitude.. In other words values of direction and magnitude of electric force
If we make some changes to our coulomb law equation then we have

This expression is unit vector that has a direction from charge Q1 to charge Q2 and is denoted as 12 which means charge Q1 applies the force on charge Q2
If we have positive results from the equation we can say that forces are repulsive and for opposite charges or attraction forces minus sign will exist

Limitations of Coulomb’s Law

There are some limitation this law have described here
It is used for static charges not for moving charges
It is used to find the forces between charges that have a regular shape not used for irregular shapes
The formula of this law is used only if molecules of solvent among the particles are larger than both charges
Where inverse square law is applied it used

That is all about the coulomb’s law all details has explained if you have any questions ask here

Author: Henry

http://www.theengineeringknowledge.com

I am a professional engineer and graduate from a reputed engineering university also have experience of working as an engineer in different famous industries. I am also a technical content writer my hobby is to explore new things and share with the world. Through this platform, I am also sharing my professional and technical knowledge to engineering students.

Originally published at https://www.theengineeringknowledge.com on November 26, 2022.