Page 6 - Electrostatics 11

Grade 11 © GC Shiba
Distribution of charge over the surface of conductor

☻ When a body is charged, the charge spreads all over the surface of the body

which may or may not be uniform.
☻ The distribution of charge depends upon the shape of the conductor.
☻ The greater the curvature at any point, the greater will be the accumulation of
charge.

Types of charge distribution:
1. Linear charge density (λ ): The charge per unit length of a body is called
linear charge density. i.e., λ =q/l

The charge distributed on a very thin straight rod.
2. Surface charge density (σ ): The charge per unit area of a body is called
surface charge density. i.e., σ =q/A
The charge distributed uniformly on a thin disc.

3. Volume charge density (ρ ): The charge per unit volume is called volume
charge density. i.e., ρ = q/V

The charge distributed inside a spherical non-conducting body.

Action of points:

The leakage of charge from sharp points is called action of point.
☻ The distribution of charge over the surface of a conductor is uniform

only when the surface is uniform shaped.
☻ The density of charge at any part of
conductor is inversely proportional to the

radius of curvature of the surface of that part.

i.e., (σ = ⟹ ∝ )

☻ It is greater on those parts of the surface

which have the greater curvature (least radius of curvature).
☻ Hence, density of charge at the pointed parts of a conductor is very large.
☻ E.g., The air particles and dust particles coming in contact gain charge
from the sharp points by conduction.

Uses of Action of points:
☻ The lightning conductor are made pointed upward in order to have a safe

discharge of the electricity generated in the atmosphere.
☻ The electric poles supporting the transmission lines at high voltage are
fitted with a sharp pointed conductor at the top. If there is any leakage of
charge from the line to the poles, it is discharged into the atmosphere

through the pointed ends.
6 Electrostatics