Introduction To Electrostatics & Coulomb's Law - Field Theory.


- Electrostatics is a branch of science that involves the study of various phenomena caused by electric charges that are slow-moving or even stationary.


- Electric charge is a fundamental property of matter and charge exist in integral multiple of electronic charge. Electrostatics as the study of electric charges at rest.


- The two important laws of electrostatics are
  • Coulomb’s Law.
  • Gauss’s Law.

- Both these laws are used to find the electric field due to charge configurations.


- Coulomb’s law is applicable in finding electric field due to any charge configurations where as Gauss’s law is applicable only when the charge distribution is symmetrical.


COULOMB’S LAW:

- Coulomb’s law is the “Law of Action” which describes the force between two point charges.


- A point charge is a charge that occupies a region of space which is negligibly small compared to the distance between the point charge and any other object.


- Coulombs law states that “ The force of attraction or repulsion between two point charges Q1 and Q2 is:
  • Proportional to the charges Q1 and Q2.
  • Varies inversely as the square of distance between them.
  • Acts along the line joining the two point charges.

- Mathematically, Coulomb’s law is expressed as:






Where k is the proportionality constant and is defined as












εo is known as the permittivity of free space and εr is called the relative permittivity of any dielectric material.

In Free Space, εr = 1, hence








Hence equation of force in free space becomes:



Introduction To Electrostatics & Coulomb's Law - Field Theory.

- Here the diagram represents the coulomb 
vector force on Point charges Q1 and Q2.



Force F12 on Q2 due to Q1 is given as:




















- Similarly F21 on Q1 due to Q2 is given as:

F21 = |F12 | aR21 = |F12 | ( - aR12 )
F21 = - F12 since [aR21 = - aR12 ]


- The force on Q1 due to Q2 is equal in magnitude but opposite in direction to the force on Q2 due to Q1.


- If there are more than two point charges, then the principle of Superposition can be used to determine the force on a particular charge.

If there are N numbers of charges Q1, Q2, Q3…..Qn located respectively at points with position vectors r1, r2, r3….rn, the force experienced by a charge Q located at position vector r is given as:








ALSO READ:

- Electric Field Intensity (E).

- Electric Lines Of Forces /Streamlines / Electric Flux (ψ) .

- Electric Flux Density (D).

- Electric Field Intensity Due To a Finite and Infinite Line Charge.

- Electric Field Intensity Due To a Infinite Sheet Charge.

- Electric Field Intensity Due To a Circular Ring Charge.

- Electric Field Intensity Due To a Circular Disk Charge.

- Numericals / Solved Examples - Electric Force and Field Intensity.

- Numericals / Solved Examples - Electric Field Intensity - Line, Surface and Mixed Charge Configuration.

- Short Notes/FAQ's

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