View source for Permittivity of free space

[[Category:Done 2018-06-01]] 
<onlyinclude>The '''permittivity of free space''', '''ε<sub>0</sub>''', is a physical constant used often in [[electromagnetic force|electromagnetism]]. It represents the capability of a [[vacuum]] to permit [[electric field]]s. It is also connected to the [[energy]] stored within an electric field and [[capacitance]]. Perhaps more surprisingly, it's fundamentally related to the speed of light.</onlyinclude> The permittivity of free space, '''ε<sub>0</sub>''', is defined as:<Ref name=hyp>Hyperphysics. (August 27, 2015). ''Electric and Magnetic Constants'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elefie.html</ref> 

<center><math>\epsilon_0 = \frac{1}{\mu_0 c^2}\approx8.8542 \times 10^{-12} </math> F/m ([[farad]]s per [[meter]])</center>

where 

*<math>\mu_0</math> is the [[permeability of free space]] and
*<math>c</math> is the [[speed of light]].

An electric field, <math>E</math>, in a region of space has field energy associated with it, that [[energy density]] is:<ref>Jackson, John David (1998). Classical Electrodynamics (3rd ed.). New York: Wiley. p. 213</ref>
<center> <math>\frac{Energy}{volume}= \frac{\epsilon_0 E^2}{2 } </math></center>

The energy stored in a [[capacitor]] (with no [[dielectric]]) is:

<center>Energy <math> = \frac{\epsilon_0 A}{2d} V^2</math></center>

where

*<math>A</math> is the area of the plates,
*<math>d</math> is the distance between the plates
*<math>V</math> is the [[voltage]] between the plates.


The permittivity of free space can also be used to find the [[Coulomb force]]. The constant gives how strong the [[force]] is between two [[charge]]s separated by a distance:<ref name=hyp/>

<center><math>F = \frac{1}{4 \pi \epsilon_0} \frac{q_1 q_2}{r^2}</math></center>

where

*<math>F</math> is the Coulomb force,
*<math>q_1</math> and <math>q_2</math> are two charges, and
*<math>r</math> is the separation between the charges.

== For Further Reading ==
For further information please see the related pages below:
*[[Permeability of free space]]
*[[Electric field]]
*[[Photon]]
*[[Capacitor]]
*Or explore a [[Special:Random|random page]]


==References==
{{reflist}}