ε₀ measures how easily an electric field forms in vacuum. A medium with dielectric constant K has ε = Kε₀.
Value of ε₀ in different units
| Value | Use it when |
|---|---|
| 8.854 × 10⁻¹² C² N⁻¹ m⁻² (or F/m) | SI. |
| 8.988 × 10⁹ ≈ 9 × 10⁹ N m² C⁻² (1/4πε₀) | Coulomb's law constant, used far more often. |
Formulas that use ε₀
- F = (1/4πε₀) q₁q₂/r²
- C = ε₀A/d
- c = 1/√(μ₀ε₀)
Its dimensional formula is worked out on the dimensional formula of permittivity of free space ε₀ page.
Other constants
- Gas constant (R): 8.314 J mol⁻¹ K⁻¹
- Planck's constant (h): 6.626 × 10⁻³⁴ J s
- Avogadro's number (Nₐ): 6.022 × 10²³ mol⁻¹
- Speed of light (c): 3 × 10⁸ m/s
- Charge of an electron (e): 1.602 × 10⁻¹⁹ C
- Mass of an electron (mₑ): 9.109 × 10⁻³¹ kg
- Mass of a proton (mₚ): 1.673 × 10⁻²⁷ kg
- Mass of a neutron (mₙ): 1.675 × 10⁻²⁷ kg
- Universal gravitational constant (G): 6.674 × 10⁻¹¹ N m² kg⁻²
- Acceleration due to gravity (g): 9.8 m/s²
- Boltzmann constant (k): 1.381 × 10⁻²³ J/K
- Faraday constant (F): 96 485 C/mol
- Permittivity of free space (ε₀): 8.854 × 10⁻¹² C² N⁻¹ m⁻²
- Permeability of free space (μ₀): 4π × 10⁻⁷ T m/A
- Rydberg constant (R): 1.097 × 10⁷ m⁻¹
- Stefan–Boltzmann constant (σ): 5.67 × 10⁻⁸ W m⁻² K⁻⁴
- Wien's constant (b): 2.898 × 10⁻³ m K
- Bohr radius (a₀): 0.529 Å
- Molar volume of a gas at STP (Vₘ): 22.4 L/mol
The full list, searchable, is on the physical constants page.
Questions students ask
What is the value of permittivity of free space?
ε₀ = 8.854 × 10⁻¹² C² N⁻¹ m⁻². In other units: 8.854 × 10⁻¹² C² N⁻¹ m⁻² (or F/m); 8.988 × 10⁹ ≈ 9 × 10⁹ N m² C⁻² (1/4πε₀).
What is ε₀ in physics and chemistry?
ε₀ measures how easily an electric field forms in vacuum. A medium with dielectric constant K has ε = Kε₀.
Which value of ε₀ should I use?
8.854 × 10⁻¹² C² N⁻¹ m⁻² (or F/m): SI. 8.988 × 10⁹ ≈ 9 × 10⁹ N m² C⁻² (1/4πε₀): Coulomb's law constant, used far more often.
What is the dimensional formula of permittivity of free space?
See the dimensional formula of permittivity of free space, worked out step by step on its own page.