Name for 1/(4πε₀)? What is the Meaning?

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Discussion Overview

The discussion revolves around the constant 1/(4πε₀), often referred to as the Coulomb constant, and seeks to clarify its naming, meaning, and relationship to various unit systems in physics.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • Some participants identify the constant as the Coulomb constant due to its appearance in Coulomb's Law.
  • Others argue that the constant k arises from a mismatch of units in the SI system and is related to c², with powers of ten introduced due to this mismatch.
  • A participant notes that Gaussian units do not include a constant in the expression for electric potential, suggesting that most physicists prefer this system for practical work.
  • One participant claims that ε₀ is not related to the permittivity of free space, despite common textbook definitions lacking explanation.
  • Another point raised is that Coulomb's Law is a specific case of Gauss's Law, with the factor of 4π resulting from integrating the electric field over a sphere's surface area.
  • It is mentioned that the value of ε₀ varies depending on the unit system used, with SI, Gaussian, and Heaviside-Lorentz systems being the most common.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation and significance of the constant, with no consensus reached regarding its naming or the implications of its value across different unit systems.

Contextual Notes

The discussion highlights limitations in definitions and assumptions regarding the constant's meaning and its dependence on the chosen unit system, without resolving these issues.

brian0918
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Has a name been given to this constant? The most I've seen is calling it k, but is there another name for it, or any statement for understanding its meaning (such as how e0 can be called the "permittivity of vacuum")?
 
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It's called the Coulomb constant because it appears in Coulomb's Law.
 
The constant k appears because of a mismatch of units in the SI system.
It is related to c^2, but powers of ten come in because of the mismatch.
Gaussian units, in which V=q/r with no constant, is used by most working physicists in their own work. epsilon0 has nothing to do with the permittivity of free space, although all elementary texts do call it that, never with an explanation because there is none. Most graduate texts still use Gaussian units.
 
Couloumbs law is a special case of Gauss law. The factor of 4[itex]\pi[/itex] is due to the integration of the electric field over the surface area of a sphere. In the more general Gauss law, only the factor of [itex]\epsilon_0[/itex] is present.

Claude.
 
The value of [itex]\epsilon_0[/itex] depends solely on the system of units used. The three most common systems used these days are the SI system, the Gaussian (or cgs) system, and the Heaviside-Lorentz (HL) system.
 

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