The picofarad per meter (symbolized pF/m) is a unit of electric permittivity , a constant of proportionality that exists between electric displacement and electric field intensity.

Permittivity is a characteristic of matter , and is important in the design and construction of capacitor s and radio-frequency ( RF ) transmission lines. The permittivity of a vacuum (also known as free space) is equal to approximately 8.85 pF/m.

Relative permittivity can be expressed as the ratio of the number of picofarads per meter in a particular substance to 8.85 pF/m. This ratio is called the dielectric constant of a material. Free space has a dielectric constant of 1, and most substances have a dielectric constant greater than this.

Also see capacitance , permittivity , SI , and Table of Physical Units and Constants.

*This was last updated in*March 2011

*Posted by:*Margaret Rouse

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