• Support PF! Buy your school textbooks, materials and every day products Here!

Griffiths page 150

  • Thread starter ehrenfest
  • Start date
  • #1
2,012
1
[SOLVED] Griffiths page 150

Homework Statement


Please stop reading unless you have Griffith's E and M book.

On this page, Griffith's start talking about "pure" and "physical" dipoles. Can someone define what these terms mean?


Homework Equations





The Attempt at a Solution

 

Answers and Replies

  • #2
siddharth
Homework Helper
Gold Member
1,127
0
Isn't it explained pretty clearly in the same page?

A physical dipole (one with a finite separation between charges)
Where exactly are you having difficulty?
 
Last edited:
  • #3
D H
Staff Emeritus
Science Advisor
Insights Author
15,393
682
A physical dipole comprises a pair of equal but opposite charges [itex]q[/itex] separated by a vector [itex]2a\hat r[/itex]. The dipole moment is [itex]2aq\hat r[/itex]. By decreasing the separation distance but increasing the charge you can keep the dipole moment constant. A pure dipole has a zero separation distance but a non-zero dipole moment. Such a thing is not physically realizable.
 
  • #4
pam
455
1

Homework Statement


Please stop reading unless you have Griffith's E and M book.

On this page, Griffith's start talking about "pure" and "physical" dipoles. Can someone define what these terms mean?
What G means in Ex. 3.8 is that the point charges example is one physical configuration that has a dominant dipole moment. He seems to define a "pure" dipole as a configuration that has ONLY a dipole moment, and no higher moments. As he says, that point charges model is only a "pure" dipole in the limit -->0. The sphere with with cos charge distribution is a pure dipole because its potential for r>R is pure dipole.
None of this is too clear in G because he does not discuss higher dipole moments in good detail. Some things are clearer in more advanced texts.
 
  • #6
511
1
DH and pam explained nce...

You may try to get a copy of Corson and Lorrain for more rigorous treatment of higher terms.
 

Related Threads for: Griffiths page 150

  • Last Post
Replies
13
Views
2K
  • Last Post
Replies
9
Views
2K
  • Last Post
Replies
6
Views
2K
  • Last Post
Replies
2
Views
1K
Replies
4
Views
505
  • Last Post
Replies
5
Views
2K
  • Last Post
Replies
3
Views
3K
  • Last Post
Replies
2
Views
3K
Top