Permittivity | Wikipedia audio article
Channel: wikipedia tts
Date: 24/12/2018

This is an audio version of the Wikipedia Article:
https://en.wikipedia.org/wiki/Permittivity


00:02:45 1 Units
00:04:03 2 Explanation
00:05:45 3 Vacuum permittivity
00:08:16 4 Relative permittivity
00:11:51 5 Practical applications
00:12:01 5.1 Determining capacitance
00:13:18 5.2 Gauss's law
00:17:50 6 Dispersion and causality
00:18:59 6.1 Complex permittivity
00:19:46 6.2 Tensorial permittivity
00:19:50 6.3 Classification of materials
00:27:09 6.4 Lossy medium
00:28:10 6.5 Quantum-mechanical interpretation
00:28:37 7 Measurement
00:29:28 8 See also
00:33:02 9 Notes
00:35:00 10 References
00:36:46 11 Further reading



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SUMMARY
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In electromagnetism, absolute permittivity, often simply called permittivity , usually denoted by the Greek letter ε (epsilon), is the measure of capacitance that is encountered when forming an electric field in a particular medium. More specifically, permittivity describes the amount of charge needed to generate one unit of electric flux in a particular medium. Accordingly, a charge will yield more electric flux in a medium with low permittivity than in a medium with high permittivity. Permittivity is the measure of a material's ability to store an electric field in the polarization of the medium.
The SI unit for permittivity is farad per meter (F/m or F·m−1).
The lowest possible permittivity is that of a vacuum. Vacuum permittivity, sometimes called the electric constant, is represented by ε0 and has a value of approximately 8.85×10−12 F/m.
The permittivity of a dielectric medium is often represented by the ratio of its absolute permittivity to the electric constant. This dimensionless quantity is called the medium’s relative permittivity, sometimes also called "permittivity". Relative permittivity is also commonly referred to as the dielectric constant, a term which has been deprecated in physics and engineering as well as in chemistry.

  
    
      
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    {\displaystyle \kappa =\varepsilon _{r}={\frac {\varepsilon }{\varepsilon _{0}}}}
  By definition, a perfect vacuum has a relative permittivity of exactly 1. The difference in permittivity between a vacuum and air can often be considered negligible, as κair = 1.0006.
Relative permittivity is directly related to electric susceptibility (χ), which is a measure of how easily a dielectric polarizes in response to an electric field, given by

  
    
      
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    {\displaystyle \chi =\kappa -1}
  otherwise written as

  
    
      
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    {\displaystyle \varepsilon =\varepsilon _{\mathrm {r} }\varepsilon _{0}=(1+\chi )\varepsilon _{0}}