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Permittivity - The Electrostatic Connection

written by: Ricky • edited by: Lamar Stonecypher • updated: 7/23/2008

Permittivity or dielectric constant of a material is an important property of materials from the electrical engineering perspective. Find out what is exactly meant by this and how is it useful in practical applications.

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    We know that when a voltage is applied across a conductor it results in the flow of electrons which we call current. But what happens when the same voltage is applied across a dielectric material which does not allow for easy flow of current? You can imagine a similar situation in mechanics that when you compress a gas like say a balloon filled with air, it simply shrinks to accommodate for the force, but a solid substance develops stress inside it since it cannot change its volume. Something similar happens in this case as well

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    The Electrostatic Connection

    Permittivity of a material is its ability to store electrostatic energy whenever a voltage is applied across the material. Each material of medium is supposed to have two kinds of permittivity namely absolute and relative.


    Absolute permittivity is the permittivity of free space or perfect vacuum (though this term is ambiguous as this state cannot be achieved practically), while relative permittivity is the permittivity of the material when compared with the absolute permittivity. The value of absolute permittivity is 8.854 * 10-12 F/m which stand for farads/meter.


    The relative permittivity of a material is also known as the dielectric constant and gives a measure of the electrostatic energy storage capacity of the medium


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    Uses of Dielectric Materials


    You surely must have heard about capacitors and a basic capacitor is nothing but an arrangement where two conducting materials have a dielectric material place in between. Voltage is applied across the conducting plates which results in the storage of electrostatic energy in the dielectric medium and the amount of the energy stored depends on several factors such as the applied voltage, dielectric constant of the material and so forth. Of course there are several other uses of dielectric material and their properties of storing electrostatic energy.

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    An Interesting Observation

    I would like to bring to your notice one important and interesting observation now that we are dealing with electrostatics here. It is not directly related to the dielectric properties but is surely related to electrostatics, hence the reason to include it here.


    We know from our study of the Coulomb's law in a separate article that we can calculate that the force exerted by two charged particles on each other. Let us calculate the same for alpha particles (we can use any other particles for calculation purposes) and from the equation of Coulomb's law we can see that it is of the order of 9.2 * 10-2 Newtons


    If we compare this to the force of gravitation between these particles, it comes out in the range of 3 * 10-37 Newtons (I have deliberately avoided the mathematics here). This shows that the gravitational force is nearly negligible as compared to the electrostatic force between these particles. This just goes to show the power of the electrostatic forces.