A point charge inside infinite medium of dielectric

[Ready2GoXtr]

A point charge inside infinite dielectric material

1. The problem statement, all variables and given known data
A point charge is an infinite medium of dielectric material having a relative permittivity [tex]\epsilon_r[/tex]. <--- epsilon(sub r). Find the electric field vector and the potential function at any point in space, assuming that the potential is zero volts at infinity.

Homework Equations

D = $$\epsilon$$ * E + P
P = [tex]\epsilon₀[/tex] * [tex]\chi_e[/tex] vector E
[tex]\epsilon[\tex] = [tex]\epsilon₀[/tex] * [tex]\epsilon_r[/tex]
[tex]\chi_e[/tex] = [tex]\epsilon_r[/tex] - 1


well its not letting me put it in right so I am going to enter them in with () next to them
D(vector) = epsilon*E(vector) + P(vector)
P(vector) = epsilon(sub 0)*chi(sub e)*E(vector)
epsilon = epsilon(sub 0)*epsilon(sub r)
chi(sub e) = epsilon(sub r) - 1
Electric Field of Point Charge = k*q/r^2
Electric Field of Sphere = q/(4*pi*epsilon(sub0)*r^2)

The Attempt at a Solution

Im not quiet sure what my first step would be. I would think that a point charge inside a dielectric medium would have a reduced electric field, but it is infinite so wouldn't its electric field be nothing?

 

[gabbagabbahey]

Just use Gauss' Law for $\textbf{D}$...can you think of a Gaussian surface that will exploit the symmetry present?

 

[Ready2GoXtr]

what do you mean by exploit?

 

[gabbagabbahey]

"Exploit" is just another word for "use"

 

[Ready2GoXtr]

I feel that a sphere represents a good shape.

 

[gabbagabbahey]

I feel that a sphere represents a good shape.

Okay, but why? And where will the center of the sphere be?

 

[Ready2GoXtr]

The center of the sphere will be located on the point charge

 

[Ready2GoXtr]

so would my answer just be q/(4*pi*epsilon(sub0)*r^2)
?

 

[gabbagabbahey]

Not quite...What is Gauss' Law in terms of $\textbf{D}$? Do you see why Gauss' Law in terms of $\textbf{E}$ isn't helpful here?