Relative Permittivity

by Ancho
Tags: permittivity, relative
Ancho is offline
Oct25-13, 10:51 PM
P: 1
Hello forum members,

I am trying to wrap my head around the concept of relative permittivity. I have read the Wikipedia article on the subject, but I don't feel quite satisfied. As far as I understand it, RP is essentially a measure of how well a given material holds a static charge relative to a vacuum, which makes it similar to conductance, resistivity and dielectric strength, no? If not, how exactly is it related to those concepts?

Another thing I don't quite understand is how RP relates to capacitance. For instance, let's say I have two small, geometrically identical spheres with a 10cm diameter. According to the calculations from wolfram alpha, each sphere will have a self-capacitance of 5.563 picofarads, but these calculations don't take into account the nature of the material of the spheres. What if one is made of a material with a very high permittivity, like 10,000, while the other is made of a material with a permittivity of 10? Would that not change the capacitance values of the spheres quite drastically?

The whole subject feels like soup in my head at the moment . Help with clearing up these concepts would be highly appreciated.
Phys.Org News Partner Engineering news on
New ultrasound device may add in detecting risk for heart attack, stroke
Enhanced ground control system and software for small unmanned aircraft
SensaBubble: It's a bubble, but not as we know it (w/ video)
NascentOxygen is offline
Oct26-13, 01:00 AM
HW Helper
P: 4,717
Hi Ancho.

Permittivity is not related to dielectric strength or resistivity. Think of a parallel plate capacitor, with a vacuum or dry air gap between the plates. If you fill the air gap with a material having relative permittivity of 4, then the capacitance (the number of charges the plates store for a given potential difference) goes up by that same factor of 4.

Register to reply

Related Discussions
relative permittivity of a conductor Introductory Physics Homework 19
calculating the relative permittivity of a material Advanced Physics Homework 0
Non-linear relative permittivity in Maxwell Engineering Systems & Design 0
Can there be a material with relative permittivity < 1? Classical Physics 1
Relative permittivity/Permeability General Physics 13