Electrostatic energy of a dielectric sphere

  • Thread starter libelec
  • Start date
  • #1
176
0
1. Find the electrostatic energy of a neoprene sphere or ratio R, charged with Q if:

a) Q is uniformly distributed in surface



The Attempt at a Solution



So, I can calculate the displacement field (so that I can use the expresion U= [tex]\int \vec{D}.\vec{E} dV[/tex]), but only for those points in space where r>R. Then, given that D=[tex]\epsilon[/tex]E, I can find the electric field for r>R.

But I don't know how to get the electric field inside the sphere, since D=0 there because there're no free charges inside. It could also happen that E doesn't exist inside the sphere either, but I woundn't know the reason why.

Any ideas? Thanks.
 

Answers and Replies

  • #2
176
0
Anybody?
 
  • #3
176
0
Does anybody know how I can get P of polarization?
 
  • #4
gabbagabbahey
Homework Helper
Gold Member
5,002
6
[
So, I can calculate the displacement field (so that I can use the expresion U= [tex]\int \vec{D}.\vec{E} dV[/tex]), but only for those points in space where r>R.
How are you calculating the displacement field? And why can't you calculate it for [itex]r\leq R[/itex]?

Then, given that D=[tex]\epsilon[/tex]E, I can find the electric field for r>R.
doesn't [itex]\epsilon=\epsilon_0[/itex] for [itex]r>R[/itex]?

But I don't know how to get the electric field inside the sphere, since D=0 there because there're no free charges inside. It could also happen that E doesn't exist inside the sphere either, but I woundn't know the reason why.
You've already given the reason why.....just assume that neoprene is a linear dielectric, then you know [itex]\textbf{D}=\epsilon\textbf{E}[/itex], so if [itex]\textbf{D}=0[/itex], then so does the electric field!
 
  • #5
176
0
Yes, thank you. I thought I had to find the polarization vector P.
 

Related Threads on Electrostatic energy of a dielectric sphere

Replies
5
Views
44K
Replies
3
Views
328
Replies
2
Views
4K
  • Last Post
Replies
2
Views
269
  • Last Post
Replies
11
Views
981
  • Last Post
Replies
2
Views
1K
Replies
1
Views
1K
Replies
1
Views
658
Top