Electric Charge & Its Nature-Coulomb’s Law

Coulomb’s law is a basic fundamental law in electrostatics. According to Coulomb’s law:

• It depends on the magnitude of the product of the charges between two particles.
• On the other hand, the interaction force is directly proportional to the two points (If we take the two-point charges as q1,q2 )

Mathematically, it can also be expressed as:

F=K*q1*q2/r2

Where F is the force,k is a constant known as electrostatics constant, and its value is:

9*109 Nm²C-²

q1 , q2 represents the magnitude of charges present in the bodies.

Units and dimensions:

The Coulomb’s force is nothing but a fundamental force in nature; hence its SI unit is also given by Nm²Kg-²

Its dimension is given by:

[MLT-2]

Critical features of Coulomb’s law:

1. The force between two bodies depends inversely on the square of the distance between two objects.
2. The shape and size of the bodies are not necessary if the distance between their centre of mass remains constant.
3. The value of electrostatics constant k depends on the nature of the medium present between two bodies and the system of units chosen.
4. The force tends to diminish with increasing distance and tends to be 0 at infinitely large separation.
5. The value of the term k/r2 remains constant for any two bodies.
6. Coulombs’ force can assume both positive and negative quantities. If the two bodies have opposite charges, then the value of the force is negative and hence the force is attractive. On the other hand, if the two charges are of the same sign, then the value of F is positive, indicating repulsive force.
7. Coulombs’ force of attraction is among the five fundamental forces of the universe and is 1035 times stronger than the gravitational force.

Limitations of Coulomb’s law:

1. Coulomb’s law is applicable only when the two bodies are point charges and does not have any other shape. For example, it does not give any direct relationship for the force of attraction between two bars. Other methods like integration etc., needed to be applied to get the force of attraction between them.
2. It is challenging to use Coulomb’s law when the bodies assume any irregular shape.
3. The law cannot be applied satisfactorily for substantial objects since a large body means there is a difference between the body’s boundaries.

Important remarks:

1. Coulomb’s law has been verified over many bodies, including atomic and subatomic particles, from a microscopic distance. The law proved to be valid.
2. Coulomb’s law is similar to Newton’s law of gravitational force between two bodies. i.e 
3. The electrostatic force of attraction and repulsion is far more potent than the gravitational force of attraction.
4. Whereas the gravitational force can only be attractive, Coulomb’s force can be both attractive and repulsive in nature.

Dielectric constant(k):

The dielectric constant k that appears in Coulomb’s law of attraction is an important parameter determining the force of attraction between two bodies.

Suppose q1, q2 be two charges present at a distance of r from each other. So as per Coulomb’s law, the force of attraction between two bodies is given by:

F=1/4π६*q1q2/r²

Now, if the medium is not a vacuum, then the force of attraction is given by:

F0=1/4πε*q1q2/r²

Dividing the equations, we get F0/F=K, say

This k is also known as the dielectric constant in Coulomb’s law.

The dielectric constant of any medium is defined as the ratio of the force of interaction between two point charges separated by specific distances in air/vacuum to the force of interaction they experience when they have the same distance of separation in that medium.

Its value is always more than or equal to 1. (1 when the medium is a vacuum)

Conclusion:

Coulomb’s law is a fundamental force of the universe. It depicts the force of interaction between charge bodies. Coulomb’s law states that the force of interaction between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between the two charged bodies. It also depends on the medium present between the two point charges. Coulomb’s force of attraction can be both positive and negative. Whereas the Positive sign indicates that the force of attraction is repulsive, the native sign indicates that the force of attraction is attractive. Nm2Kg-2 gives SI units of Coulomb’s force. It is addictive and hence can be extended to multiple point charges. Its dimension is given by [MLT-2].

The Coulomb force is similar to the gravitational force but is much stronger than it. It can be both repulsive and attractive, unlike the gravitational force, whereas the gravitational force can only be attractive.