Page 27 - Electrostatics 11

Grade 11 © GC Shiba
☻ State Gauss law of electrostatics and use it to find the electric

field intensity due to a plane charge conductor.

Electric intensity due to charged plane conductor

Let us consider a positively charged

plane conductor having surface charge
density σ .( σ = charge/surface area). We
are interested to find the electric intensity at
point P outside the charged plane conductor

at a distance r. A cylindrical Gaussian
surface of cross-sectional area A through P
is drawn as shown in figure.

The total electric flux passing through the
Gaussian surface is = .
Since net charge enclosed by the area A is σ A, so by Gauss's theorem,
ℎ
=
∈ 0

, . =
∈ 0

=
0
This is the required expression for electric intensity due to the charged plane

conductor.

Electrostatic shielding: The electric field inside a conductor or cavity is always

zero which is not influenced by external electric field whatever be the charge and

field configuration outside (the region where no electric shock is experienced due
to zero potential). This is known as electrostatic shielding. E.g., a car has a hollow

metallic body and we remain safe inside it due to electrostatic shielding during
thunderstorm and lightning.

Zero potential: If a body can either supply or absorb any amount of charge without

charge in electric potential, it is said to be at zero potential. Electric potential of

earth is said to be zero potential. It is reference potential.

27 Electrostatics