Coulomb’s law

Introduction

In general Coulomb law is the mathematical definition of force among charged items. It was built in the 18th-century by French physicist Charles-Augustin de Coulomb, similar to Isaac Newton’s law of gravity.

Both gravitational and electric forces are reduced with the square of the distance between objects, and both forces operate along a line between them. In Coulomb’s law, however, the magnitude and the sign of the electric force are not by the mass of an object. 

Therefore, charge determines how electromagnetism affects the movement of charged particles. Charge is generally the basic asset of a matter. Every part of a matter has an electric charge with a value that can be positive, negative, or zero. 

For example, electrons are negatively charged, and atomic nuclei are positively charged. In Most cases the bulk matter has an equal amount of positive or negative charge and therefore has zero net charge.

Coulomb’s Law

The law states that the magnitude of the electrostatic force of attraction or repulsion between any two point charges is directly proportional to the product of the magnitude of Charges and is inversely proportional to the square of the distance between them.

Generally Coulomb’s law says that the interaction between charged objects is a non-contact force that acts over some distance of separation.

Suppose that if we had two charged bodies, one positive and the other negative charge, they would pull each other if kept at a certain distance from each other. Now if we increase the charge of one body to keep the other unchanged, the force of attraction obviously increases.

Similarly, if we increase the charge of the second body to keep the first one unchanged, the attraction force between them again increases. Therefore, the force between charged bodies is proportional to the charge of either body or both.

                                          F∝Q1 and F∝Q2==>F∝Q1Q2

Mathematically:

Mathematically, Coulomb’s Law is expressed as:

|F|=k|q1q2|r2

Where,

q1 and q2 are the charges and d is the distance between them.

k is proportional constant known as coulomb constant and is (ke ≈ 8.988×109 N⋅m2⋅C−2)

According to Coulomb, the electric force for charges at rest has the following properties:

• Generally like charges repel each other; and the unlike charges attract each other. Therefore, the two negative charges repel each other, while the positive charge attracts a negative charge.
• Attraction or repulsion acts along the line between the two charges.
• Force size varies inversely as the square of the distance between the two charges. Hence, if the distance between the two charges is doubled the attraction and repulsion becomes weaker. Decreasing one-fourth of the original value. When the charge approaches 10 times, the magnitude of the force increases by 100 times.
• The size of the force is directly proportional to the value of each charge. The unit used to measure the charge is coulomb (C).

Limitations:

There are three conditions that must be true for Coulomb’s inverse Square Law:

• Charge must have a spherical symmetric distribution.(e.g. be a point charge, or a charged metal sphere).
• The charges must not overlap on each other.
• The charges must be static with respect to each other.

Some other Limitations:

• Coulomb law is valid, if the Average number of solvent molecules between the two charged particles is large.
• Coulomb’s law is true, if the point charges are at rest.
• It is difficult to apply Coulomb’s law when the charges are in arbitrary shape. Hence, we cannot evaluate the value of distance between the charges when they are in arbitrary shape.

Conclusion

In this Article we have studied Coulomb’s law. This law is also known as inverse Square Law and helps us to find the force between two charged particles which are at rest or are Static in nature. According to Coulomb’s law, the force of attraction or repulsion between two charged bodies is directly proportional to the product of their charges and inversely proportional to the square of distance between them.