Surface Charge of Uniformly charged sphere

Click For Summary
SUMMARY

The discussion centers on the concept of surface charge in the context of a uniformly charged solid sphere, as presented in Griffiths' "Introduction to Electrodynamics." Participants clarify that a uniformly charged sphere does not have a surface charge in the same way a conducting sphere does. The key distinction is that surface charge refers to a finite amount of charge on an infinitely thin layer, while a uniformly charged sphere has a consistent charge density throughout its volume. This leads to the conclusion that the electric field remains continuous at the surface of a uniformly charged solid sphere, contrasting with the discontinuity observed in the presence of a surface charge.

PREREQUISITES
  • Understanding of electric fields and charge distributions
  • Familiarity with Griffiths' "Introduction to Electrodynamics"
  • Knowledge of the differences between conducting and non-conducting spheres
  • Basic concepts of electrostatics and Gauss's law
NEXT STEPS
  • Study the concept of electric field continuity and discontinuity in electrostatics
  • Learn about charge density and its implications in different geometrical configurations
  • Explore the differences between conducting and non-conducting materials in electrostatics
  • Investigate the mathematical derivation of electric fields for uniformly charged spheres
USEFUL FOR

Students of electromagnetism, physics educators, and anyone seeking to deepen their understanding of electrostatic principles and charge distributions.

teroenza
Messages
190
Reaction score
5

Homework Statement


In the section on the discontinuity of the electric field (Griffiths introduction to electrodynamics) there is the following.

"Where there is no surface charge, the perpendicular component of the electric field (to the surface) is continuous, as for instance at the surface of a uniformly charged solid sphere.

This is as opposed to being discontinuous, by σ/ε_0 when a surface charge exists

Homework Equations





The Attempt at a Solution


If it was a conducting sphere, I would understand that if it was neutral, there would be no net charge on the surface, but I do not see why it has to be the case here.
 
Physics news on Phys.org
It doesn't say the sphere is conducting. A "uniformly charged sphere" means the charge density in each part of the sphere is the same. A conducting sphere can't be that. All of the charge would move to the surface.
 
Ok. But because it is uniformly charged, there is presumably a nonzero charge density on the surface (as elsewhere) and thus charge on the surface.

I just don't understand why the surface of a uniformly charged solid sphere has no charge on it. That is contradictory. I'm not sure if I am not understanding the physics or the words.

Why is "...surface of a uniformly charged solid sphere." and example of a place ""Where there is no surface charge'''?
 
teroenza said:
Ok. But because it is uniformly charged, there is presumably a nonzero charge density on the surface (as elsewhere) and thus charge on the surface.

I just don't understand why the surface of a uniformly charged solid sphere has no charge on it. That is contradictory. I'm not sure if I am not understanding the physics or the words.

Why is "...surface of a uniformly charged solid sphere." and example of a place ""Where there is no surface charge'''?

You misunderstand what 'surface charge' is. Surface charge is (ideally) a finite amount of charge contained in an infinitely thin layer, the surface. It's a useful idealization to make for a conducting sphere which has no charge in the interior and all of its charge very close to the surface. Very different from a 'uniformly charged sphere'.
 
Last edited:
teroenza said:
Ok. But because it is uniformly charged, there is presumably a nonzero charge density on the surface (as elsewhere) and thus charge on the surface.

I just don't understand why the surface of a uniformly charged solid sphere has no charge on it. That is contradictory. I'm not sure if I am not understanding the physics or the words.

Why is "...surface of a uniformly charged solid sphere." and example of a place ""Where there is no surface charge'''?

Imagine the surface as a shell of one atom (molecule) thick. The radius of an atom is about 10-10 m. How much is the charge of the shell compared to the charge of a sphere of radius R=0.1 m?

In case of a metal, all charge accumulates in that surface shell.

ehild
 

Similar threads

  • · Replies 4 ·
Replies
4
Views
2K
Replies
4
Views
4K
  • · Replies 49 ·
2
Replies
49
Views
6K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 1 ·
Replies
1
Views
6K
Replies
12
Views
1K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K