Chapter 20
Electric Field
Syllabus 3 hrs
Electric field due to point charges; Field lines
Gauss Law: Electric Flux
Application of Gauss law: Field of a charge sphere, line charge, charged plane conductor
Electric Field
The space around charge where its effect (force of attraction or repulsion) can be experienced is called
electric field. The effect may be strong or weak. Theoretically, electric field extends up to infinity. However,
in practice it becomes inappreciable after certain distance.
In general, there are two quantities at each point of electric field. They are electric potential and electric
field intensity.
Electric Field Intensity
The electric field intensity at the point in electric field is defined as the force experienced by unit positive
test charge kept at that point. It is also called electric field strength or electric field.
Let is the force experience by unit positive test charge in the electric field, then the electric field
intensity is given by
It is the vector quantity and its direction is along which the positive charge tends to would move.
Unit:
SI unit: or or
Dimension:
[ ] [ ]
[ ] [ ]
[ ] [ ]
Types of Electric Field
1. Uniform Electric Field
If the magnitude and direction of electric field intensity remains constant throughout in the certain region,
the electric field is said to be uniform.
2. Non-uniform Electric Field
If the magnitude or direction or both of electric field intensity varies from point to point, the electric field is
said to be non-uniform.
Electric Field Intensity due to Point Charge
Consider the point charge at point in the space. Let the test
charge is placed at point at distance from point . The force
experienced by test charge is given by
Hence, the electric field intensity at point is given by
This gives the magnitude of electric field intensity. Its direction is in the direction of electrostatic force .
Electric Field Lines (Elecric Lines of Force)
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Electric Field
Syllabus 3 hrs
Electric field due to point charges; Field lines
Gauss Law: Electric Flux
Application of Gauss law: Field of a charge sphere, line charge, charged plane conductor
Electric Field
The space around charge where its effect (force of attraction or repulsion) can be experienced is called
electric field. The effect may be strong or weak. Theoretically, electric field extends up to infinity. However,
in practice it becomes inappreciable after certain distance.
In general, there are two quantities at each point of electric field. They are electric potential and electric
field intensity.
Electric Field Intensity
The electric field intensity at the point in electric field is defined as the force experienced by unit positive
test charge kept at that point. It is also called electric field strength or electric field.
Let is the force experience by unit positive test charge in the electric field, then the electric field
intensity is given by
It is the vector quantity and its direction is along which the positive charge tends to would move.
Unit:
SI unit: or or
Dimension:
[ ] [ ]
[ ] [ ]
[ ] [ ]
Types of Electric Field
1. Uniform Electric Field
If the magnitude and direction of electric field intensity remains constant throughout in the certain region,
the electric field is said to be uniform.
2. Non-uniform Electric Field
If the magnitude or direction or both of electric field intensity varies from point to point, the electric field is
said to be non-uniform.
Electric Field Intensity due to Point Charge
Consider the point charge at point in the space. Let the test
charge is placed at point at distance from point . The force
experienced by test charge is given by
Hence, the electric field intensity at point is given by
This gives the magnitude of electric field intensity. Its direction is in the direction of electrostatic force .
Electric Field Lines (Elecric Lines of Force)
1|Page
