Themes > Science > Physics > Electromagnetism > Electrostatics > Permittivity > Permittivity of the Medium

Now we will proceed with our discussion for the equivalent case in the medium.

In a medium (i.e. some kind of material), the value of k is smaller than its value in air or vacuum. In a medium, it is conventional to take

,

where e is called the Permittivity of the medium and has the same dimensions as the permittivity of the vacuum, C²/N·m².

Definition:

Dielectric constant, k, of a medium: k = e / e₀ = k₀ / k

Obviously, the Coulomb force is smaller in the medium by a factor k as compared to the vacuum value. (k is a Greek letter and pronounced "kappa".) For all materials, we have

Let's look at some typical value for the dielectric constant:

You can see that typical values for solids are between 1 and 10, and for liquids between 10 and 100. But for certain substances, we can also reach values of k up to 1000 or even 10000.

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