Relative Permittivity: Exploring Static Charge & Capacitance

In summary: This is because the permittivity indicates how well the material will concentrate electric flux lines between the plates. The permittivity of a material is the ratio of the electric flux density to the electric field strength within the material.In summary, relative permittivity is a measure of how well a material can hold a static charge compared to a vacuum. It is not related to dielectric strength or resistivity. In terms of capacitance, filling the space between plates of a parallel plate capacitor with a material of higher permittivity will increase the capacitance by that same factor.
  • #1
Ancho
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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 :confused:. Help with clearing up these concepts would be highly appreciated.
 
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  • #2
Hi Ancho. http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]

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.
 
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1. What is relative permittivity?

Relative permittivity, also known as dielectric constant, is a measure of the ability of a material to store electrical energy in an electric field. It is the ratio of the electric flux density in a material to the electric flux density in a vacuum.

2. How is relative permittivity related to static charge?

Relative permittivity is related to static charge through the concept of capacitance. Capacitance is the ability of a material to store electrical charge. The higher the relative permittivity of a material, the higher the capacitance and the more charge it can store.

3. What factors affect the relative permittivity of a material?

The relative permittivity of a material is affected by its chemical composition, molecular structure, and temperature. The type and concentration of atoms or molecules in a material and the arrangement of these particles can greatly influence its relative permittivity.

4. How is relative permittivity measured?

Relative permittivity is typically measured using a device called a capacitance meter. This device measures the capacitance of a material and uses it to calculate the relative permittivity. Another common method is to use a parallel plate capacitor and measure the capacitance with different materials placed between the plates.

5. Why is relative permittivity important in practical applications?

Relative permittivity is important in many practical applications, such as in the design of electronic devices and circuits. It allows engineers to select materials with the desired capacitance and electric field characteristics for specific purposes. It also plays a crucial role in understanding the behavior of insulating materials in high voltage applications.

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