Relative Permittivity

Description:

Relative permittivity is given by the ratio of absolute permittivity to the permittivity in free space.

ε_r = ε_a/ε_o

Where

• ‘ε_r’ is the relative permittivity.

• ‘ε_a’ is the absolute permittivity.

• ‘ε_o’ is the permittivity in free space.

Above equation can be written as : ε_a = ε_r . ε_o

We know that Columb force (F)

F = 1/4πε q₁q₂/r²

• More the permittivity of medium, less is the force on charges in the medium.

Now, Force charge in medium is given by −

F = 1/4πε_rε_a q₁q₂/r² .....(1)

And force is free space given by −

F = 1/4πε_o q₁q₂/r² .....(2)

On dividing the two we get

F_o/F_m = ε_r or F_m = F_o/ε_r

So, we can say, Force in q medium is equal to the force in o free space divided by the permittivity of medium.

Note − 1. Relative permittivity for free space is always 1.

2. Relative permittivity for any other medium is always greater than 1.

3. For any medium other than air, the force between the particles always decreases.