State Coulomb’s law.

Short Answer

Coulomb’s law explains the force between two electric charges. According to this law, the electric force between two charged objects is directly proportional to the product of their charges and inversely proportional to the square of the distance between them. This force acts along the line joining the two charges.

Coulomb’s law also states that like charges repel each other and unlike charges attract. It helps us calculate the strength of electric forces in electric fields, circuits, and many physical processes involving charged particles.

Detailed Explanation :

Coulomb’s Law

Coulomb’s law is a fundamental rule in electrostatics that describes how electric charges interact with each other. It was proposed by French scientist Charles-Augustin de Coulomb in the 18th century. This law forms the basis of understanding electric forces, electric fields, and many modern technologies like capacitors, electric circuits, and electronic devices.

Coulomb’s law provides a mathematical way to calculate the magnitude of force between two charges. The electric force acts on each charge due to the presence of another charge and is similar in nature to gravitational force but is much stronger. While gravitational force always attracts, electric force can either attract or repel.

Statement of Coulomb’s Law

Coulomb’s law states:

“The electric force between two point charges is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.”

Mathematically,

Where:

  • F = electric force between the charges
  • q₁ and q₂ = magnitudes of the two charges
  • r = distance between the charges
  • k = Coulomb’s constant

The force acts along the straight line joining the two charges.

Nature of Force in Coulomb’s Law

The force described in Coulomb’s law has some important characteristics:

  1. Like Charges Repel

If both charges are positive or both are negative, the force is repulsive.

  1. Unlike Charges Attract

If one charge is positive and the other is negative, the force is attractive.

  1. Force Acts Along the Line Joining the Charges

Coulomb’s force is a central force, meaning it acts directly between the two charges.

  1. Force Depends Only on Distance and Magnitudes

The medium between the charges can affect the force, but the simple form applies in vacuum or air.

Meaning of the Formula

The formula tells us four important things:

  1. Directly Proportional to Charges

If either charge is increased, the electric force increases.

  1. Inversely Proportional to Distance²

If the distance doubles, the force becomes one-fourth.

  1. Stronger Than Gravity

Electric forces are extremely strong compared to gravitational force between two masses.

  1. Predictable Behaviour

We can calculate the force exactly using the formula.

This makes Coulomb’s law extremely useful in physics and engineering.

Point Charges in Coulomb’s Law

Coulomb’s law applies best to point charges, which are small charged particles whose size is much smaller than the distance between them. Examples include:

  • Electrons
  • Protons
  • Small charged spheres

Larger bodies with distributed charge can also be analysed using this law by breaking them into smaller charge elements.

Effect of Medium on Coulomb’s Force

Although the basic formula applies to vacuum, in real life, charges are often placed in air, water, glass, or other materials. The medium reduces the electric force depending on its permittivity.

Force becomes:

Where  is the permittivity of the medium.

In vacuum,

Thus, Coulomb’s law helps us understand forces in different materials.

Applications of Coulomb’s Law

Coulomb’s law is widely used in physics and engineering:

  1. Electric Field Calculations

Electric fields around charges are found using Coulomb’s law.

  1. Behaviour of Charges in Circuits

It helps predict how charges will move in wires and components.

  1. Capacitor Design

Electric force between charged plates is calculated using this law.

  1. Chemistry and Atomic Structure

Attractive forces between electrons and protons follow Coulomb’s law.

  1. Particle Physics

Motion of charged particles in electric and magnetic fields is based on this force.

  1. Understanding Static Electricity

When clothes stick or sparks occur, Coulomb’s force is involved.

Importance of Coulomb’s Law

Coulomb’s law is extremely important because:

  • It explains electric interactions between particles.
  • It forms the foundation of electrostatics.
  • It helps engineers design electronic devices.
  • It connects electricity, magnetism, and atomic structure.
  • It allows accurate prediction of electric forces in all situations.

Without Coulomb’s law, understanding electricity would be impossible.

Conclusion

Coulomb’s law gives a clear mathematical rule to calculate the electric force between two charges. The force is proportional to the product of the charges and inversely proportional to the square of the distance between them. It helps explain why charges attract, repel, and influence each other. This law is fundamental in understanding electric fields, circuits, atomic structure, and many modern technologies.