Is There a Constant Parallel to ε0 in Gauss's Law in cgs?

Click For Summary

Homework Help Overview

The discussion revolves around the concept of permittivity in the context of Gauss's Law, specifically questioning whether there is a constant parallel to the permittivity of free space (ε0) in the cgs system. The subject area includes electrostatics and the comparison of units between the SI and cgs systems.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the relationship between Coulomb's law and Gauss's Law in both SI and cgs units, questioning the necessity of a constant similar to ε0 in the cgs framework. Some participants express uncertainty about the integral involved in Gauss's Law.

Discussion Status

The discussion is ongoing, with participants sharing their interpretations of the equations and the implications of unit systems. Some guidance is offered regarding the application of Gauss's Law and the nature of electric fields, but no consensus has been reached on the existence of a constant parallel to ε0 in cgs.

Contextual Notes

There appears to be confusion regarding the integral in Gauss's Law and the correct formulation of Coulomb's law in cgs units. Participants are also navigating the differences in definitions and constants between the two systems.

Karol
Messages
1,380
Reaction score
22

Homework Statement


Is there a constant parrallel to the ε0 permittivity in the Gauss law in c.g.s?

Homework Equations


Coulomb force in m.k.s: ##F=\frac{1}{4\pi\varepsilon_0}\frac{qq'}{r^2}##
Coulomb force in c.g.s: ##F=\frac{qq'}{r^2}##
Gauss's law in m.k.s: ##\frac{N}{A}=\varepsilon_0 E##

The Attempt at a Solution


The Coulomb's constant k was transformed to ##\frac{1}{4\pi\varepsilon_0}## in order that the number of field lines N extruding from a surpace round a point charge will equal the net chrage inside the surface:
\frac{N}{A}=\varepsilon_0 E\rightarrow \frac{N}{4\pi r^2}=\varepsilon_0 \frac{q}{4\pi\varepsilon_0 r^2}\rightarrow N=q
So the ##\frac{1}{4\pi}## term was chosen for that in order to cancel with the area of a sphere.
I think, in order that N=q will be also in c.g.s we also need ##\frac{1}{4\pi}## term:
Coulomb's law in c.g.s: ##F=\frac{1}{4\pi B}\frac{qq'}{r^2}\rightarrow \frac{1}{4\pi B}=1##
 
Physics news on Phys.org
In the cgs system, the Coulomb force is ##F=\frac{q_1 q_2}{r^2} ##,
ε0=1, D=εE in materials, D=E in vacuum.
Gauss' Law for a single point charge in vacuum ##\oint{E_n dA} = 4\pi q_{enclosed}##
 
I don't know yet this integral.
So i am right, right? Coulomb's law in c.g.s: ##F=\frac{1}{4\pi}\frac{qq'}{r^2}##
 
Karol said:
I don't know yet this integral.
So i am right, right? Coulomb's law in c.g.s: ##F=\frac{1}{4\pi}\frac{qq'}{r^2}##
No. ##F=\frac{qq'}{r^2}##
The electric field around a point charge q is radial, and the magnitude is E=q/r2. Integrating is to a sphere of radius r, with the charge in the centre is (4πr2)E = 4πq
 

Similar threads

Replies
6
Views
2K
  • · Replies 18 ·
Replies
18
Views
1K
Replies
4
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 10 ·
Replies
10
Views
4K
Replies
11
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
Replies
10
Views
4K
Replies
23
Views
5K
  • · Replies 3 ·
Replies
3
Views
2K