# Pls explain me permittivity

Electrical permittivity...in mathematical terms, i.e I need the derivation...WITHOUT using 'curls'.

Didn't find it online.

## Answers and Replies

The permittivity of a medium is a constant that is connected to the electrical properties of that medium.Amongst other places it appears in Coulombs law and along with permittivity( a magnetic constant ) the formula for the speed of light.

The permittivity of a medium is a constant that is connected to the electrical properties of that medium.Amongst other places it appears in Coulombs law and along with permittivity**( a magnetic constant ) the formula for the speed of light.
In mks units, the capacitance of a rectangular capacitor of relative permittivity e, separation d, and area A is

C = e e0 A/d Farads

where e is relative permittivity (unitless)
e0 is the permittivity of free space, 8.85 x 10-12 Farads per meter.

**The magnetic constant is permeability.

In mks units, the capacitance of a rectangular capacitor of relative permittivity e, separation d, and area A is

C = e e0 A/d Farads

where e is relative permittivity (unitless)
e0 is the permittivity of free space, 8.85 x 10-12 Farads per meter.

**The magnetic constant is permeability.
Thank you Bob I got my mittivity mixed up with eability.I would blame it on the beer but I haven't had one yet.

I'm asking the derivation of permittivity, not relative.

And pls explain a bit of theory also.

Born2bwire
Science Advisor
Gold Member
What do you mean derivation? I'm not aware of any derivation of permittivity or permeability from first principles, at least not classically. The two are constants. Permittivity can be thought of as describing the capacitance of the medium. Even vacuum can be thought of as having a capacitance. In a material, the permittivity describes the ability to store extra energy. This is done by polarizing the molecules in the material. The induced dipoles allow you to store more energy in the material.

In my opinion, permittivity can be defined as the ability of a medium to allow conductors at an electric potential to accumulate electrical charges on it's surface.