Electric field direction and permittivity

Click For Summary

Discussion Overview

The discussion revolves around the direction of the electric field and how it is influenced by permittivity when a test charge is placed near a polarized material. Participants explore the implications of material properties on the behavior of electric fields, particularly in relation to test charges positioned at various locations relative to the material's surface.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that the electric field direction can be measured by the force on a test charge, suggesting that the presence of a polarized material alters this direction.
  • It is suggested that the force on a test charge near the surface of a polarized material will point more perpendicular to the surface due to the influence of polarized particles.
  • One participant questions whether the effect of permittivity can indeed change the direction of the force on the test charge.
  • Another participant affirms that the effect is possible and inquires about the calculability of this effect, drawing a parallel to Snell's law.
  • A later reply discusses boundary conditions for electromagnetic fields, indicating that the electric field components are continuous across the boundary and suggesting a relationship similar to Snell's law.
  • One participant seeks clarification on whether the force on a test charge inside the material points directly towards the main point charge, indicating uncertainty about the influence of the material.
  • Another participant counters that the direction of the force inside the material will also be altered by the material properties.
  • One participant expresses a desire for additional resources or links regarding the calculation of how the force direction changes within the material.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the specifics of how permittivity affects the direction of the electric field. There are competing views on the nature of the force direction inside the material and the applicability of Snell's law-like principles.

Contextual Notes

Participants reference boundary conditions and the relationship between electric field (E) and electric displacement field (D), but there are unresolved assumptions regarding the specific calculations and conditions under which these principles apply.

zrek
Messages
115
Reaction score
0
The electric field direction can be measured by the force affected on a test charge.

Let's put a point-like charge not far from a material, that is polarized by it.
See the figure:
permittivity1.png

The test force on the test charge A points exactly to the charge.

I think that because the surface is full of polarized particles in one direction, the test charge next to the surface (C) will behave differently, the force on it will points more perpendicular to the surface.

And also the inner test charges (like B) will be under the effect of the neighbour particles, so the direction of the force will point a little towards the surface.

Is this effect possible? Can the permittivity affect to the direction of the force?

Thank you for your toughts.
 
Physics news on Phys.org
The test force on the test charge A points exactly to the charge.
There should be a slight deviation due to the material below it.
Is this effect possible? Can the permittivity affect to the direction of the force?
Yes it can.
 
mfb said:
Yes it can.

Is it calculatable somehow? For example like the Snell's law?
 
With the boundary conditions for electromagnetic fields - the parallel component of E and the perpendicular component of D are continuous, the field inside the material and outside are divergence-free, and D and E are proportional to each other* with some material constants.

For the surface, this should give something similar to Snell's law I think.

*there are materials where this is not true. It does not change the basic concept, however.
 
mfb said:
... the field inside the material and outside are divergence-free...

Am I understand it well that inside the material the force on the test charge points (in avarage) exactly to the main point-charge?
 
No, the direction there will be changed by the material, too.
 
I googled the net, but I have not found relevant information about this. Please if anyone have a link about the calculation of how the force direction change inside the material, share this info, I'd be happy.
Thank you in advance!
 

Similar threads

Undergrad Does path independence still hold if permittivity is non-uniform?
  • · Replies 18 ·
Replies
18
Views
2K
Undergrad Work done by electric field of an irregularly shaped conductor
  • · Replies 3 ·
Replies
3
Views
2K
High School Electric Field Direction: Are We Assuming a Universal Positive Frame?
  • · Replies 20 ·
Replies
20
Views
3K
High School Understanding the electric field
  • · Replies 16 ·
Replies
16
Views
2K
Undergrad How does permittivity in Coulomb's law work?
  • · Replies 5 ·
Replies
5
Views
2K
Undergrad Tangential electric force at a surface
  • · Replies 3 ·
Replies
3
Views
2K
Undergrad How Does Each Element in the Permittivity Tensor Matrix Represent an Anisotropic Material?
  • · Replies 9 ·
Replies
9
Views
6K
Undergrad Does a time varying magnetic field in vacuum produce electric field or not?
  • · Replies 7 ·
Replies
7
Views
2K
Undergrad Magnetic field as result of length contraction
  • · Replies 20 ·
Replies
20
Views
5K
High School Direction of Electric Field & Field Due to a Dipole
  • · Replies 5 ·
Replies
5
Views
4K