This presentation explains Electrostatic Fields and covers following topics: -Electrostatic Field -Coulomb's Law -Electric Field Intensity -Electric Flux Density -Gauss's Law -Electric Potential -Electric Dipole -Electric Flux -Equipotential Surfaces This presentation is as per the course of DAE Electronics ELECT-212.

1. ELECTROSTATIC FIELD
Irfan Sultan
Instructor (Telecom.)
Govt. College ofTechnology

2. OBJECTIVES
 State Coulomb’s Law and Field Intensity
 Describe Electric Field due to continuous charge distribution formulas
 Discuss Electric Flux Density
 Describe Gauss’s Law and its application to a point charge
 State Electric Potential
 Describe Relationship between E &V
 Discuss Electric Dipole
 Discuss Electric Flux Lines and Equipotential Surfaces

3. ELECTRIC FLUX DENSITY
 Definition: A measure of the intensity of an electric field generated by a free
electric charge, corresponding to the number of electric field lines passing
through a given area.
 It is also called electric displacement.
 If Electric Field Strength (E) is multiplied by the permittivity (𝜀) of a material, the
resulting value is called Electric Flux Density (D).
 Its unit is Coulombs/m2
 Formula: D = ε𝐸
 Where, 𝐸 =
𝑄
ε𝐴

4. DIFFERENCE B/W
ELECTRIC FLUX (𝜓) AND
ELECTRIC FLUX DENSITY (𝐷)
 The Electric Flux is a measure of the Electric Field due to some charge,
experienced over a hypothetical surface area of any magnitude. The Electric Flux
Density is a measure of the Electric Field due to some charge, experienced over a
hypothetical Unit surface area i.e. 1 square units.

5. GAUSS’S LAW
APPLICATIONTO A POINT CHARGE
 The Electric Flux leaving a closed surface is Proportional to the charge enclosed.
𝜓 ∝ 𝑄

6. ELECTRIC POTENTIAL
 Electric potential is the amount of work needed to move a unit positive charge
from a reference point (taken at infinity i.e. beyond the influence of electric field)
to a specific point in an electric field.
𝑉 =
𝑊
𝑞
=
𝑭. 𝒓
𝑞
=
𝑘𝑄
𝑟
 Unit: J/C (Joules per Coulomb)

7. ELECTRIC POTENTIAL DIFFERENCE
 It is the work done to move a unit charge from one point to
another in an electric field.
𝑉𝐴𝐵 = 𝑉𝐴 − 𝑉𝐵 =
𝐴
𝐵
𝐸. 𝑑𝑙 =
𝑊
𝑄

8. ELECTRIC DIPOLE
 An electric dipole is a separation of positive and negative charges. The simplest
example of this is a pair of electric charges of equal magnitude but opposite sign,
separated by some (usually small) distance. A permanent electric dipole is called
an electret.

9. ELECTRIC FLUX LINES

10. ELECTRIC FLUX LINES: QUIZ
 Fill in the blanks in the associated
diagrams with appropriate letters, A
to J, depending on the amount of
charge on each object.

11. EQUIPOTENTIAL SURFACES
 Equipotential surfaces are surfaces of constant scalar potential.
 In electrostatics, the work done to move a charge from any point on the
equipotential surface to any other point on the same equipotential surface is zero
since they are at the same potential.

12. EQUIPOTENTIAL SURFACES: EXAMPLES

13. EQUIPOTENTIAL SURFACES: EXAMPLES