*Electrostatics - Coulomb's Law*, Coulomb's Law was defined aswell as the Electric Field Strength.

If we take the Vector quantity

**E**which is the electric field strength (a vector as it has both magnitude and direction) and multiply it by the permittivity ε, we get a new vector

**D.**

So

**D**= ε

**E =**ε * Q/4π ε r2 , the ε cancles out leaving us with D = Q/4π r2

Notice how the electric flux density is independant of the permittivity ε. What does this mean?

Well say we had an electric field acting on a type of material, then from the formula for the electric field strength we know that the value of

**E**is dependant upon the material used by the value of the permittivity ε. But the electric flux density

**D**will remain the same no matter what material you use.

Basically although changing the types of materials will effect the electric field strength

**E**, it will not affect the electric flux density

**D**.