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Grade 11 © GC Shiba
1) Electric intensity inside a charged conducting solid sphere
Consider a charge conducting sphere of radius R
having a charge +Q. We are interested to find the electric
intensity at point P inside a charged sphere. Let us draw a
concentric sphere of radius r through point P. This sphere is P
called a Gaussian sphere.
By symmetry, electric intensity would be the same at all
points on the surface of a Gaussian sphere. Electric flux from
the charged sphere is radially outward as shown in the
figure.
Now, electric flux passing through the gaussian surface is
ℎ
=
∈ 0
=E . A
or, E . A = 0 ( since no charge is enclosed by
gaussian surface)
E = 0
Hence, there is no electric field inside the charged sphere.
2) Electric intensity outside a charged conducting sphere
Consider a charge conducting sphere of radius R
having a charge +Q. We are interested to find the electric
intensity at point P outside a charged sphere. Let us draw
a concentric sphere of radius r through point P. This
sphere is called a Gaussian sphere.
By symmetry, electric intensity would be the same at all
points on the surface of a Gaussian sphere. Electric flux
from the charged sphere is radially outward as shown in
the figure.
Now, electric flux passing through the gaussian surface is
ℎ
=
∈ 0
23 Electrostatics
